Xperia X8 :: No Internet And Phone Shuts Down With Other Sim Cards?

I have recently bought a Xperia X8 in New Zealand. It was sold in the Vodafone phone section of an electronic store, the salesperson assured me it was not locked to Vodafone so I decided to buy it and take it back home with me to Samoa. Prior to departing for Samoa, I've used the phone with a Vodafone NZ sim card for about a week, everything worked fine, internet, GMail, apps market, apps etc.After arriving back in Samoa, I hooked it up to my computer to update the phone software which included an upgrade to Android 2.1. After that, I took it down to a Digicel (one of the two mobile phone service providers in Samoa) store to get my internet set up. After leaving the store I've realised only the browser's internet connection worked, but no internet connection for of the apps, apps market, GMail etc...

(1)No internet Did some research on the net about this problem, tried getting the wizard back up and signing into my google account, no luck. Formatted the phone, tried to set up my google account straight away in the wizard, no luck. Digicel doesnt know what's wrong either. There are no Android phones currently sold by Digicel in Samoa so I guess I can't really blame them. It's very frustrating. Fortunately, I've been able to hook up the phone to my home's wifi connection, internet works fine of course...the apps, the apps market, GMail etc.

(2) Phone shuts down with other sim cards Ever since having taken the phone down to the Digicel store (they took it to the back so I don't know what else they did with the phone) to get the internet set up, no other sim cards work with the phone. Well they work, but, only a few seconds or at most a minute after entering the sim pin, then the phone just goes blank and reboots itself. This happens with simcards from the other mobile phone service provider (tried both mine and my dad's) AND with the Vodafone sim card I used in NZ!?!?! Could Digicel have done something to the phone which makes it shut down when non-Digicel sim cards are inserted?