Do while loops with chars

So here I have a do-while loop. When I push a button, then press enter, the program should do stuff, then ask me for another key. If I press any key but q, it repeats itself. If I press q then enter, it should end the loop. But then when I press q then enter, it still does the functions in the do-while loop. How do I solve this problem?

Java Code:

Scanner kb = new Scanner(System.in);
System.out.print("Press any key to start.");
String letter = kb.next();
do
{   
   stuff
   System.out.print("Press any key to call another number or press \"q\" to quit.");
   letter = kb.next();
}while(!letter.equals("q") || !letter.equals("Q"));