Hi davidigross,
Sorry to hear you have had your iPhone 7 stolen, I've been in a similar situation and its an awful feeling!
I assume you have already contacted AppleCare in regards to what options you have (if any) in terms of securing your device. If not, here is an article that covers some of the steps you can take.
My recommendation would be;
- To contact your phone provider and have the devices IMEI number blocked, so that it is unable to be used by another person for calls or messages.
- Contact local law enforcement and register your devices IMEI/Serial number as stolen, so that if it is found they can contact you.
- Put your device into 'Lost Mode' if it is signed into an iCloud account and Find My iPhone is enabled.
Do rest assured that if you had a passcode enabled on your device, your data will be safe, as the phone will only enable 10 attempts at guessing your passcode, after which it will disable itself and secure all of the encrypted contents.
In terms of the cost of the phone that you are still paying off, it is unlikely that you will be able to halt payments on the device. But because of the significance of the money to you, I would recommend contacting the company directly that you purchased the device on a plan from, and they will be able to provide you with your options.
Best of luck, I hope something works out for you!