On Airtv Bullying me

I have a contract with On Airtv for an explorer, which they charge me R169. Lately I have been getting call from their agent saying I have not been paying for the last 3 months. I explained to them that I have been paying because every month on the 25th a debit order goes through to their account which they have set-up from their side. I only had to approve the debit order instruction with my bank. The agent whom sounds like a lady is very rude and threatening me that they will handover my account. When I asked why they believe they have not been getting payment from me, the lady agent tells me that they have had a system issue from their side. I have called them and whenever you select the billing department number from the auto machine the phone get dropped. I have send them two emails and they have not responded to any of them. I do not appreciate being threatened, is though I am the one who cause they system failure. Worse is the the debit order continues to go through every month since the inception of the contract.