Problem using my mobile metatrader4 the first time.

this is a question.  when I try to log into my fxchoice account on my smartphone for the first time.  I only get prompted with numbers and my user name is letters.  Of course, I might be able to just change my user name to numbers however, that is like giving up.  I'm wondering why I'm not prompted with letters on my metatrader 4 login screen.  I do get more interesting after this !!!