What's wrong with my phone? (t-mobile pre paid)?

[Lilly loves lobster]

I tried to refill the minutes but it wouldn't let me, it kept saying something like "This is not a time fill number or the phone has been de activated" but not in those words of course but it was something like that, How do i re activate my phone? i didn't use it for about 5 months or so but how do i re-activate it?

 

[Salamander]

You might have to get a new sim card. My mom had a problem similar to that and that is what she had to do.