Thread: My first OOP

hi guys, would just like your thoughts on my first object orientated program of a ATM machine. also theres a little prob, it doesnt seem to deduct money from the account.

Code:

#include <iostream>
#include <stdlib.h>

using namespace std;

class ATM
{
      private:
      int CardNumber, PinNumber;
      int Balance;
      
      public:
      void EnterCard();  
      void SetBalance();
      void ShowBalance();
      void DrawMoney();
      void DispenseMoney(int Amount);                                   
};

//------------------------------------------------------------------
ATM ATM1;  
//------------------------------------------------------------------   
 
void ATM::SetBalance()
{
     cout << "How much do you want in your account? " << endl;
     cin >> ATM1.Balance;
     
     cout << "Balance is now; " << ATM1.Balance << endl;
     system("pause");
}
//-----------------------------------------------------------------          
void ATM::EnterCard()
{
     cout << "Card Number : ";
     cin >> ATM1.CardNumber;
     
     cout << "Pin Number  : ";
     cin >> ATM1.PinNumber;
}
//------------------------------------------------------------------
void ATM::DrawMoney()
{
     int Amount;
     cout << "How much money would you like: ";
     cin >> Amount;
     
     if(Amount > ATM1.Balance)
     {
                cout << "Sorry, you do not have enough funds" << endl;
     }
     else {ATM1.DispenseMoney(Amount);}
}
//--------------------------------------------------------------------
void ATM::DispenseMoney(int Amount)
{
     ATM1.Balance - Amount;
}
//-------------------------------------------------------------------
void ATM::ShowBalance()
{
     cout << "Your balance is: " << ATM1.Balance << endl;
     system("pause");
}
     
//---------------------------------------------------------------
int main(int argc, char *argv[])
{
 int Menu;
 
ATM1.EnterCard();
ATM1.SetBalance();

while(Menu != 3)
{           
 cout << "1) Display Balance, 2) Draw Money out, 3) Exit : ";
 cin >> Menu; 
 
 switch(Menu)
{
             case 1:
                  {
                    ATM1.ShowBalance();  
                    break;        
                  }
             case 2:
                  {
                    ATM1.DrawMoney(); 
                    break;        
                  }
}

 Menu = 0;
 system("cls");
}//while != 3 
 
 return 0;   
}

thanks,