How to get internet on my blackberry?

I have a Verizon Blackberry Tour & its unlocked so I am using it for at&t. When I go to Verizon they can't do anything & when I go to at&t they won't touch the phone because its Verizon. I have tried so much to figure out how to get internet on this phone & I just can't do it. I really need internet on my phone & I can't send MMS messages either. Is there a number I can call or something to contact someone so I can get internet & be able to send MMS messages? Leave links or numbers, thanks so much!(: