Automatic payments Resulted in 3 years OVERPAYMENT.

This was just discovered when I had to replace my Visa card due to security concerns. This resulted in auto payments disruption due to a new card number. This then resulted in T-Mobile unable to get our payments sent me a text about “disruption in surface” without correcting the problem. Went into nearest store front and was helped in resetting my auto payments but discovered my over payment problem. Over three years back I was told about a car feature service that I accepted for our (2) cars. But the next day after I returned the devices to the store where I bought them and said “no thank you, we don’t need this”. But the $15 dollars per month charges were never removed, that amounted to $30 per month for 2021, 2022, 2023, and so far 2024. I was told by one of the Sales Persons that when I returned the (2) car devices I should have called in and stopped the charges. But I was never told that this was a requirement. It seems to me that when I returned the TWO DEVICES and because I was not told about also having to call in to cancel the automatic charges that maybe I should have the dollars returned to us by T-Mobile. The other phone is my wife’s. THANK YOU for your help with this matter!!