Cant make outgoing calls.

Hello,

In X600 , i face this issue often, cant make the outgoing calls but incoming is always works.
I need to put that SIM to other phone and then if i insert the same in my X600 , then it works.

It does some "mCheck" with the Airtel. I have opened a case with AIrtel also , but they cant help me.they say its the phone fault.

anyone face this issue ? and any known solution ..?

thanks,
ramnath
chennai