I am pondering the possibility of buying an iPhone to use on my existing T-Mobile account yet I am wondering if I am safe in doing so just in terms of service. I understand warranty and firmware risks of unlocking but because it is an unlocked phone being used on a carrier you are "not supposed" to use, is there a possibility of not being able to use the iPhone through T-Mobile in the future due to legal problems or T-Mobile deactivating your SIM?