[Miami_Son]

You shouldn't sell phones with your SIM card in them. They identify your account to the network and allow the person who has them to use your service, which you will be billed for. If you're changing carriers then remove the SIMs and destroy them. Giving them to someone else could make you liable for charges. The only thing you can clear off them is your personal info like Contact data. They will still be identifiable as far as your account is concerned.