Help Phone stuck while picking calls

[ultimate01]

Hi.

I have grand quattro. from the past one month i'm getting the problem, sometimes i cannot receive the call, if i am able to receive the call after 20-30 sec it stops responding. I cannot disconnect the call or do anything. I have to remove the battery to start using the phone again.

I reset the phone about two weeks ago, after that 1 or 2 days it was ok. Then same problem.I'm living in Rwanda, i have shown the phone to technician & he is saying that he will update the software to 4.2 & then it will be OK.

Can someone suggest me what to do ?

Thanks