I have a flexpay plan (with unlimited data) with Tmobile and the phone I use is Nokia Astound 3G. I want to get a 4G phone (Samsung Galaxy II) from Ebay or any online store but not from Tmobile store cuz they'll probably would like to change my flex pay plan as well and I don't want to do that. My question is: Can I use any 4G phone with my current flexpay unlimited web data???????