Best answer by Jonathan I
Ivan has a fairly in depth article regarding APN settings/bringing in an unlocked phone since he seems to change phones almost more than people change their underwear. Here:
MMS or BBM will work with data. BBM will also work on WiFi, unlike on legacy devices. However, if you're currently using a legacy BB (anything before the Z10/Q10, basically), any unlimited social networking or email/BBM add-ons will no longer work because the newer devices arent eligible for those anymore. You'd have to go with a "traditional" data plan.