I have a positive tab balance of $150. I'd like to use it to purchase a travel phone. Looking online, many of the phones include an "Activation Credit" if you sign up for a minimum plan. Is there a minimum commitment to that plan, and if so, how long is that commitment? What happens if you cancel early? If possible, I'd like to purchase a phone using a combination of activation credit and positive tab, so that I have no outstanding balance, and then cancel the plan immediately. The activation credit part sounds a bit too good to be true though?