Check Your Bill Balance
If you’re someone who spends a lot of time talking the phone, you’ll probably want to check your bill balance. Android owners can put in the code *225# to see how much their bill will cost. Once you dial the code, your phone should send you a message with your latest invoice.
Source: Beebom
And if you want to activate call waiting, you can do it more quickly than you thought. The code *43# will unlock your Android’s call waiting mode. When you’re done with this function, just type #43# to shut it off.