We have an old T-Mobile Motorola Razr v3 which is unlocked and use it in Thailand. My wife has a T-Mobile iPhone 5s and wants to use the Razr here in the United States. Basically, she doesn't like the iPhone, too many bells and whistles. Is it a simple matter of removing the SIM card from the iPhone and putting it in the Razr? Yeah, I know the SIMs are a different size and I have an adapter. Then if at some future date she could just swap the SIM card back to the iPhone. Anyone have any ideas on this? Thanks!