[*HELP] Can connect internet but cant connect calls!!! topic

It was just a sudden...

I can enjoy the internet service on my s5830 but mobile network unavailable.
When i call someone msg come " Mobile Network unavailable!"

But when i try to connect or use internet it gets connected and but there are no mobile signals,

I tried many sim cards in my mobile but same situation, but tried my simcard with others phones it can able to connect to calls as well!!
So, i am sure the problem is with my phone not with my sim.

So, please help me xda members!

Thanks in Advance!!