I buy unlocked phones and I use T-Mobile...never had a problem....here is some help:
1) Check and see if it is a QUAD Band phone on the noklia website
2) if it is a quad band phone the do the following:
a) go to nokiausa.com
b) click on the "support" button
c) click on set-up
d) scroll down and click "settings for browsing and MMS messaging"
e) follow the directions
ENJOY