Payment was made, but still being harassed.

I cancelled my contract in November 2022 they gave a final payment amount for the remaining months aqeelahj@ adt said payment would not be necessary to pay if the new person buying my house took over the contract. The new owner was interested took ownership in December 2022 and I was told they would inform me of the outcome. No one got back to me and I got a statement in 2023 with what I had to pay. I started paying but due to personal problems could not settle but continued to make monthly payments of R500 or more monthly end of April 2023 after my payment R864 was left and end of May 2023 it was paid and proof sent directly from my banking app I took it as closed as they previously acknowledged my previous payment without me sending pop. Since June 2023 nimble has been harassing me and I sent proof to adt again as nimble did not give a email for me to send pop. I was hasseled with calls again today. It's really annoying as this has been paid and adt is not communicating with their collectors.