I have an old phone and plan that I want to give to my son. I bought a new phone with a more upgraded plan so I would like to keep the new phone with the new plan, but under my old phone number. Is this possible? My concern if I swap the SIM card is I would get the older plan with less data, and give my son the old phone with more data. I would prefer to not lose the old plan by upgrading. Both phones are Samsung. Thanks.