Sony Ericcson P1i not detecting Kuwait Wataniya GSM network?

I purchased my Sony Ericcson P1i from India in August 2007. I live in Kuwait. After several months, the phone began re-starting spontaneously and sometimes frequently. So when I visited India in January 2008 I took it to the authorized Sony Ericcson service centre and they re-installed the software. Aftrer reaching back in Kuwait, my phone does not use Kuwait Wataniya GSM network. It detects the network, but displays "No Network". I took the phone to the authorized pesonnel in Kuwait City but they could only get me 3G network, saying that Sony Ericcson has a problem with Kuwait Wataniya. But I used to get the network before I re-installed the software. I tried updating the phone online but to no avail. I wrote to Sony Ericcson twice but they have not responded. Please advise what to do.