Pathetic service and wrong billing from Telkom

On the 2/10/ 2021 I took a contract phone with and insured it as well. I pay R389 for everything on the last day of every month. Things has been going smoothly thus far until this morning when Telkom tried to process a debit order of R700.They could not get the amount as I did not have that much money in my bank account. I then phoned call centre the first call did not go so well as gentleman that assisted me gave me an incorrect email address as I had to send him my bank statement. I had to call in again and had to explain myself all over again which I found very annoying but I didn't have the choice as I need my account to be looked into and rectified. Followed the whole process of authentication and she then went into my account to view it. I told her that when I took a contract I requested for the last day of the month to be my debit order date. Even on the 31st of Jan they deducted from my account and I even sent her my bank statement for the month of January reflecting the payment. I told her that even the invoice that they emailed me shows that I paid. So I was asking why did they deduct my account for an amount of R700 even worse as my contract is less than that amount. She told me that the debit order bounced back. I asked her how as the money went out of my account and never came back. She told me on the 3rd of February the money was reversed back into my account which I'm not aware of and why did they pay it back into my account to begin with. Now Telkom sends a meg-tape for my account to be billed on the 15th. This whole things is causing me unnecessary bank charges for their own error. The lady then asked me for a February bank statement and I told her the it does not reflect as yet on my Nedbank app. She then muted the call and eventually hung up. The service is pathetic and wish I could have a way of canceling the contract. It also affects my credit score because of their system error. I'm so annoyed to the core. Broad day light ******* as I know what I signed up for.