I have done the same previously so what happens actually when you click 1 or 2 or 3 or A..........something like you want within the Serial Port monitor then it sends the ASCII values to the arduino and not the 1 or 2 or 3 or A........... as you expected so programme your code with the ASCII values and not the keyboard value.
for example the ASCII value for 'A' is 65 and 'a' is 97 , so if you want servo to move some angle when you click 'a' programme your code with 97 as this is the value that would be sent to arduino on small 'a' input.