If you're 18 you can do a change of responsibility and the account will be put
in your name. You need to call Tmobile customer service to do this and both of
you will need to be on the call. Your best, and cheapest, bet is to stay on the family plan until your
dad can switch the plan over. You can always go to a Tmobile store or Amazon and buy a prepaid Android phone
like the LG L9 to get you through till you switch.
http://www.amazon.com/LG-Optimus-L9-Android-T-Mobile/dp/B00BMN46HW