How to delete a contract plan on a iphone 4, and also deleting it using the iphone 4?

Would you just restore it, or is there something else you do?

You can't delete a contract plan with the phone. If you are on a contract plan, you would have to contact the cell phone company you are with and talk to them on the phone or in person at their store. The only thing you can do on the iphone is to delete any apps or information on that cell phone by doing a restore through the setting icon. This will wipe all the information about the user and apps so that it is like you just got the phone on the 1st day.