Harrasment

How can I stop these fools from harassing me? Beamie ****** vehicle recovery.

In 2018 I have a vehicle covered with outsurance who they advised me that if I put a tracker recommended by them my premium will be reduced.

In 2019 I decided to sell the vehicle and I contacted beamie and told them that Iam planning to sell the car must I bring the car to them so that they can remove the tracker. The lady that I spoke to over the fone told me that it is not necessary I can sell the car she will cancel my debit on the system. I sold the car back in 2019 June but till this day they are debiting my account and the bank cant stop this debit because each month they change the reference number. I have sent them numerous emails which are not responded to. The bank advised that each time they debit I must reverse it they will eventually give up and cancel the debit but they havent , instead Iam beng harassed by their collections department and lately they have forwaded my account some lawyers whom I explained what is happening but they won't hear any of it. This is pure harrassmnet and not lawful, how do I pay for a service Iam no longer using ? and I advised the compnay before I sold the car. Can vehicle tracker ombuddmens intervene or someone advi se how do I stop these people from harrasing me. On Friday they debited R769.46 when I called the bank they revesre it and advised me that I should change the bank acount number that can be the only solution as they have tried twice already to stop hem. Ia not prepared to change the account number just for one stupid selfish company that thinks Iam a fool to pay for what Iam no longer using/ have.