T-mobile call fail/call ended

[Pegstar]

I cannot make/receive texts or calls from my iphone4. I have a t-mobile pay as you go micro sim. T-mobile 3G works fine. When I attempt to make a call it imedietly say call fail or call ended. I have contacted t-mobile and they can't seem to help me. Any1 have an idea?

 

[Gregoris]

sure you have enough credit? or are getting a good signal?