Disgusting service delivery

Im so disappointed with car tracker I took a tracker from them in 2020 then 2023 August the contract was expiring then I called them on the first week to cancel the contract ask the full balance so that I can settle the account month end I was given the discount of 50% 28September I paid the amount and send proof of payment to them and request the cancellation later and settlement letter .instead of them sending me those letters they blacklisted me demand me to pay R2700 im so disappointed on them they cant even explain why am I blacklisted disgusting poor service I will never recommend any one to then