Help ME please #FNB

I received a call, from Norman Bisset. Instructing me to pay an outstanding amount to FNB. In good faith I payed the amount requested. May 2020 payment was done. After 3 months of back and forth. Norman Bisset finally send me my paid up letter. On review I noticed this amount was settled in 2018. All I requested from the Norman Bisset was the money I paid over, and an some sort of confirmation this won’t happen again. I requested this refund in 3 October 2020. Norman Bisset is currently still escalating the situation ( seems to be a standard response ). To date I have not received anything?