Is it legal to use your old cable line to get antenna tv channels? Even if u don't receive/pay for cable tv?

We cancelled cable TV awhile back to save money. Since then we left the old cable cord plugged into the TV anyway because we discovered we can get the free antenna channels with the cable connected, but can get absolutely NOTHING without it -- because we don't have a digital converter box (no money for one... show more We cancelled cable TV awhile back to save money. Since then we left the old cable cord plugged into the TV anyway because we discovered we can get the free antenna channels with the cable connected, but can get absolutely NOTHING without it -- because we don't have a digital converter box (no money for one right now). I know antenna channels are free, but is it free to use your old comcast cable line as an antenna when you're not paying them for cable tv service? Need to know asap & really need to hear from someone who truly knows the answer and isn't guessing or assuming... because since we still get internet ONLY from comcast they have now called & said they're sending a serviceman to check out a 'problem' in our line, something about a weak internet signal... and they're coming today! :P Thanks so much anyone who knows and can help... I Googled it but just can't find an answer anywhere!
Update: We get absolutely NO cable channels, only a few free local network antenna/air channels. So we could only assume that the cable line is acting strictly as an antenna now. Thank you kindly for your fast answers!
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