i580 browser

Before I start i ran searches and did not find anything related to my question so I am sorry if I am asking a stupid question, I am new to this. My question - I have a Nextel i580 that had a broken phone clip so I used the Motorola warranty program (It was under a year old) and my phone was replaced with a new one. My phone has a web browser but I could not go to yahoo or msn to check my emails, I found out by accident that if I sent myself an email from either email account I could then browse the net through yahoo or msn and also check my mail. When I received my new phone from Motorola I just put in my sim card and everything worked as normal. I then took my phone into Nextel to have this phone registered (For warranty purposes) and I noticed that the girl turned on my phone and suddenly had a funny look on her face after poking around for a few minutes. She started typing in a bunch of codes and now I can no longer access the web like I use to. Does anyone know what she did and can I reverse it? I have two phones with Nextel and pay a lot of money to have 2000 minutes a month. I am assuming they did this to make me pay more for a data plan. Any help would be greatly appreciated.

Thank you, Billy