You can call, but the most effective way is to carry Comcast's equipment to the nearest local store and turn it back in to them. Be sure to get a receipt, and keep it forever. Also consider scanning or copying it; my shop uses thermal paper, which fades to a blank piece of paper in a week or so. Bear in mind you may be under a contract and thus subject to an early termination fee. The official word on early termination fees: http://forums.xfinity.com/t5/Billing/Early-Termination-Fees-ETF/m-p/2895117#M96760
