Refund for Non service

I cancel cable service with AT&T on February 2, 2021  when my contract end. I  request internet service ONLY..  I continue to be billed each month (March & April 2021) for service that AT&T confirmed I was cancelled. Because the ball drop on their end (AT&T), They informed me  the charges is valid and I'm not due a refund. 

I cancelled service on the day my contract end.. It's note. the person who was responsible for assuring that I was canceled did not do what was required to assure the cancellation.

I requested a transfer of service, internet only and again, the cable service continued. AT&T stole from me now $410.00 and I'm requesting it back.