I mail-ordered a refurbed iPhone 6S+ to replace my daughter's 5s that's been on StraightTalk wireless service through WalMart. It's a decent service and we intend to keep it and her #. Is is just a matter of swapping the SIM card from the 5s to the new 6s+? I've been all over the StraightTalk website and it's getting me nowhere. As you can tell, I'm not real cell-savy. Thanks!