Bought a couple of unlocked T-Mobile iPhone 6+ 128gbs for full price directly from Apple. We are currently on a three line Verizon family plan and want to switch to T-Mobile. While two of us have finished the contract, one line won't be done until December. Once we receive the new iPhone 6+s, can we use them on our Verizon plan until the last line's contract is up? Any other options?