Debit order deduction on cancelled services

I bought a fone at telkom mobile in 2015 I also took insurance at finrite which works hand in hand with telkom, I finished paying the fone on October 2017 and I requested the insurance to cancel as well on the 4th November 2017 since I was taking a new device. Finrite told me they have cancelled the insurance and their last deduction will be on the 31st December 2017. In the beginning of January 2018 I received an invoice from telkom for the new device I took but to my surprise it was still with the insurance of the previous device. I went to telkom store in Nicolway several times to report the matter, they said to me in their system it shows that the insurance is active, I asked them first of all I did not understand why is the insurance billed together with the new contract, secondly they were not helpful to me because they said I must call the insurance again and solve the matter with finite even though I told them that the consultant from finrite said the insurance is cancelled, then the last time I went there I told them I will reverse the money they debited from me and only pay for the contract I have with them and I also insisted they open a case of which they did after having to fight for them to open the case as well. Month end February I decided I will not pay the insurance so they did not receive funds from my account and I went to checkers to pay what I know is due to me excluding the insurance after a day I received a message saying my line is suspended, I went to telkom in cresta mall to enquire about this, they said to me in order for my line to be active again I should pay the insurance money, I said to them they must call finrite and confirm the cancellation since they work together, they refused and refered me to their billing department which did not help as well, they said there is nothing they can do, which did not make sense to me. I called finrite again on Wednesday fortunately I talked to a very helpful lady who finally agreed to send me an email confirming the cancellation, I see on my invoice for March I now have to pay a fee for a declined debit order, was I wrong to refuse to pay for an insurance that I cancelled and which they failed to see it's cancelled, Telkom has very nice deals but they are not helpful at all when you have problems, this issue needs to be attended to because they will loose customers due to poor service.