How do I sell my phone if it's not paid off?

The carrier of my phone line shut off my phone out of spite so I have this Iphone 7 plus 128 GB and I want to sell it now. Since it hasn't been fully paid off then it doesn't have a clean IMEI. I know the phone's worth is about $700 but what will the worth be if I jailbreak it? Any other ways I can make my phone sellable and get most of my money?

Jailbreaking won't really add to the value. It's been blacklisted so it doesn't really function as a phone anymore. Your best option is to just sell it normally and make sure to mention the IMEI has been blacklisted