I seriously doubt the OP was away from home for 9 months. A $600 bill for services reads more like 2 months.
However, the OP will have to pay the bill(s) because if plans change, you're supposed to go online and update your return date. Cox doesn't send a reminder to restore your services.
How does Cox Seasonal program work?
Enjoy the freedom of pausing your services when you're away from home for more than 30 days. Simply begin the process online, select the dates when you want to pause your services and we'll take care of the rest. Your services will automatically restore on the date you select. If your plans change, you'll be able to update the date when your services resume.