I have 3 WinMo phones (only one was bought from T-Mobile, and without a contract) and one S60 phone (bought while vacationing in Asia), and 2 lines with T-Mobile, only one of which has a data plan. If I attempt to use GPRS/EDGE/3G on the line with no data plan, I am prompted to subscribe to a data plan first, but I can still connect to WiFi APs. I have never been forced to get a data plan.
