After ending their cell phone contract, you can easily go prepaid?

My contract finished and I'd like nextel you just go pre-paid on it. "I can buy one minute to do this card. I can do this even if I cancel? Thanks in advance. I use the same phone I had with the contract. "I can cancel the service and still use Nextel phone with the same number only prepaid? Is the SIM card has nothing It's about doing this?

I like to go prepaid, with a contract that does not have to worry about adding minutes on the phone, plus evening and not late free week.

How to get free Prepaid Cell Phone Minutes