Recently, my mom upgraded from an iPhone 5 to an iPhone 6S. The SIM was left in the iPhone 5 but the phone was deactivated, new phone has its new SIM, programmed as the last one was.
1. However the last iPhone still sees Verizon LTE, 3G, etc. Why? What would happen if I tried to use these?
2. Should I take out the SIM card?
3. How does, for example, switching my SIM iinto a different Verizon phone work (Ex. The old iPhone 5).
4. Does being on contract or an installment plan change anything?
5. How does this look on the bill/online account? Will it change one of the phones to whatever the SIM went into?
I'm just generally curious if switching my SIM into a different phone will cause anything bad to happen especially while under contract/installment plan.