BB Pearl :: It Has No Internet Connection

i bought a blackberry pearl 9105 on pay as you go a few days ago. it wouldnt connect to the internet and told me to contact my service provider, which is vodafone. i took it into the shop the next morning and the guy working there proved it had nothing to do with the network by removing the sim card and putting it into another phone, which was then connecting to the internet. he told me to take my phone back to where i had purchased it from, which is argos, and they replaced the phone for me. again, same problem. i was then told to give it a few days and if theres still no progress with the connection, then they will refund it for me. it wont even connect on wi-fi. so it isnt the phone and it isnt the network, and i opted in to the blackberry services add-on, so it cant be that either.