wrong accumulated service Charge in banking system

I just made a program for banking account
But When i put initial balance let say $500 and put a "1" code to withdraw
and finally put amount of money i want to withdraw from the balance.
But ServiceCharge has to be accumulated in the CheckingAccount class but
It seems they are not accumulated in the class.
I think i made wrong loop structure but not sure what it is.

Code:

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import javax.swing.JOptionPane;


public class BankAccount {

        static CheckingAccount check;
        static String input;
        static double initialBalance;
        static double transAmount;
        static double serviceCharge;
        static double currentBalance;
        static double toServiceCharge;
        static private double below500Charge = 5.00;
        static private double below0Charge = 10.00;
        static private double checkCharge = 0.15;
        static private double depositCharge = 0.10;
        static int transCode;
       
        public static void main(String[] args) {
               
               
                initialBalance = getInitialBalance(); // get initial balance
                check = new CheckingAccount(); // create CheckAccount class
                check.setBalance(initialBalance); // pass initial balance to CheckAccount class
                transCode = getTransCode(); // get trans code
                check.setTransCode(transCode); // pass trans code to CheckingAccount class
               
                //iteration until terminate the program
               
                while(transCode == 1 || transCode == 2){ // iteration as long as trans code is 1 or 2
                       
                        if(transCode == 1){
                                transAmount = getTransAmount(); // get trans amount
                                check.setTransAmount(transAmount); // pass trans amount to CheckingAccount class
                                processChecking(); // display result of transaction
                                transCode = getTransCode(); // get trans code again to iterate the loop
                                check.setTransCode(transCode);// pass trans code to CheckingAcount class
                        }
                        else
                                processDeposit();
                }
                        processEnding();
               
        }

        public static double getInitialBalance() {
               
                double balance;
                input = JOptionPane.showInputDialog("Enter your initial balance: ");
                balance = Double.parseDouble(input);
               
                return balance;
        }
       

        public static int getTransCode() {
               
                int trCode;
                input = JOptionPane.showInputDialog("Enter the trans code: ");
                trCode = Integer.parseInt(input);
               
                return trCode;
        }
       
        public static double getTransAmount(){
               
                double tAmount;
                input = JOptionPane.showInputDialog("Enter the trans amount: ");
                tAmount = Double.parseDouble(input);
               
                return tAmount;
        }
       

        public static void processChecking() {
               
                // charge $ 5 only once when balance is below $ 500
               
                currentBalance = check.getBalance();
                serviceCharge = check.getServiceCharge();
                transAmount = check.getTranAmount();
                if(currentBalance < 500){
                                serviceCharge = below500Charge;
                                check.setServiceCharge(serviceCharge); //pass service charge to CheckingAccount class
                        if(currentBalance < 0){ // if balance is less than $ 0
                                serviceCharge += checkCharge; // when account was withdrew, service fee charged by $ 0.15
                                serviceCharge += below0Charge; // when account balance is below $ 0, service fee charged by $10
                                check.setServiceCharge(serviceCharge); // pass to CheckingAccount class
                                JOptionPane.showMessageDialog(null, "Transaction : Check in Amount of $" + transAmount +
                                                "\nCurrent Balance : $ " + currentBalance +
                                                "\nService Charge : Check --- charge $ " + checkCharge +
                                                "\nWarning balance below $ 50" +
                                                "\nService Charge : Below $ 0 --- charge $ " + below0Charge +
                                                "\nTotal ServiceCharge : $ " + serviceCharge);
                        }
                        else if(currentBalance < 50){
                                serviceCharge += checkCharge;
                                check.setServiceCharge(serviceCharge);
                                JOptionPane.showMessageDialog(null, "Transaction : Check in Amount of $" + transAmount +
                                                "\nCurrent Balance : $ " + currentBalance +
                                                "\nService Charge : Check --- charge $ " + checkCharge +
                                                "\nWarning balance below $ 50" +
                                                "\nTotal ServiceCharge : $ " + serviceCharge);
                        }
                        else if(currentBalance < 500){
                                serviceCharge += checkCharge;
                                check.setServiceCharge(serviceCharge);
                                JOptionPane.showMessageDialog(null, "Transaction : Check in Amount of $" + transAmount +
                                                "\nCurrent Balance : $ " + currentBalance +
                                                "\nService Charge : Check --- charge $ " + checkCharge +
                                                "\nTotal ServiceCharge : $ " + serviceCharge);
                        }       
                }
                else{
                        serviceCharge += checkCharge;
                check.setServiceCharge(serviceCharge);
                JOptionPane.showMessageDialog(null, "Transaction : Check in Amount of $" + transAmount +
                                "\nCurrent Balance : $ " + currentBalance +
                                "\nService Charge : Check --- charge $ " + checkCharge +
                                "\nTotal ServiceCharge : $ " + serviceCharge);
                }
        }


        public static void processDeposit() {
               
        }


        public static void processEnding() {
               
        }


}

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Code:

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public class CheckingAccount {
       
        double balance;
        double transCode;
        double transAmount;
        double totalServiceCharge;
        double serviceCharge;
       
        public void setBalance(double bal){
                balance = bal;
        }
       
        public void setTransCode(int tCode){
                transCode = tCode;
        }
        public void setTransAmount(double tAmount){
                transAmount = tAmount;
        }
       
        public void setServiceCharge(double sCharge){
                totalServiceCharge = sCharge;
        }
       
        public double getTransCode(){
                return transCode;
        }
       
        public double getTranAmount(){
                return transAmount;
        }
       
        public double getBalance(){
               
                if(transCode == 1)
                        balance = balance - transAmount;
                else if(transCode == 2)
                        balance = balance + transAmount;
                return balance;
        }
       
        public double getServiceCharge(){
                return totalServiceCharge += totalServiceCharge;
        }       
}

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Code:

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public void setServiceCharge(double sCharge){
    totalServiceCharge = sCharge;
}

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If you want the service charge to accumulate then I imagine some sort of addition would need to be performed.