cannot dial a number

[notwist]

I have an iPhone 3g. The problem is whenever I try to dial a number. When I dial each digit, it appears for a second at the top but then it disappears. I try to dial a seven digit number and call it but that doesn't work. Has anyone experienced this?

[ablach]

I am having the same problem!!!! Please tell me, where you able to solve this?

Thanks.
Andres