A:Answer I do not pay for the watch via ATT nor do I have cellular set up on the watch so I don't know how much help my answer will be. It depends on how much your watch costs. Divide the watch cost by the number of months you plan to finance it to get a primary cost, then add some for "administration" or something else to get your bill total. If you have ATT they tell you how much it will be. My watch ix 40 mm without an additional cellular line. I financed through Best Buy. Cellular option is for people who want to go without the phone and just use the watch. Not me, I can answer calls and messages without my watch without the extra. It costs $ 10 per extra line, I have 4 lines and unlimited data. you will find lots of different prices on this option. if you are running a setup like mine expect to pay abut 180 per month, depending, on insurance and a ton of other options.