I think your code is so confused here, that you need to start over with a specification, and work from that.
You need:
1. a way to start the application
2. an initial presentation of the menu items
3. establish a condition that will continue the loop within the application, and create a boolean variable for that condition:
// it has to be 'true, initially, so the while loop can start
private bool continueWhile = true;
a. similarly, you want to define what entry will terminate the loop in the application:
int terminateKeyValue = 0;
4. then you enter a while loop which starts with reading a key from the console:
a. check that key to see if it a valid entry: if not use 'continue to restart the while loop.
b. if the key is valid, and it equals in value the key you wish to terminate the application, then set 'continueWhile = false; and use 'continue to cause the while loop to execute one more time and exit.
c. given a valid key in your acceptable range of values that trigger PiggyBank methods: do the right thing to trigger the right method: I'd suggest a Switch statement to handle the different valid cases.
So your pseudo-code might look like this:
private bool continueWhile = true;
int terminateKeyValue = 0;
while(continueWhile)
{
int i =
if(iIsNotOkay(i)) continue;
if(i == terminateKeyValue)
{
continueWhile = false;
continue;
}
}