Incorrect billing

I am a very unhappy Vodacom customer. I got into a 2 year contract with vodacom for a Samsung Galaxy S8 smartphone in the 2018. I payed R710 monthly for 23 months and gave notification that I did not wish to upgrade or continue on another contract with you more than a month before the contract was due to expire. To my surprise, I got airtime on my account on the 25th month and when I called to find out why, I was told that the notification to cancel that I gave was more than 30 days so your system kicked it out (whose fault that is, I do not know), the next thing I am pulled into another 24 month contract of R170 airtime while I pay R129 pm.

Just when I am getting accustomed to this new contract I am forced into by Vodacom, last month Vodacom decides that from my account they can debit about R429. I called to find out why I now need to share my salary with vodacom and I am moved from pillar to post trying to get hold of someone who can assist me and I am given an excuse that the system activated an insurance policy on me and I had to ask if Vodacom now insures R 170 airtime with almost R300. Long story short, I reversed the debit order and manually paid R129 for the existing contract.

Today is the 7th, the date at which I must have the R129 debit order, it did not go through. I dial 135 to check my balance and the below sms is sent to me.

"Your current usage is R0 and your outstanding balance R657.38. It will be deducted 2020-10-07. For more balances dial *135# free from your phone."

I tried to resolve this last month and after speaking to five of your agents, I was told that my query has been escalated to your back office. A month later, I get the same nonsense...how far away is this back office and how many days does it take to fix the system glitches that have a bad reflection on my credit record? Getting out of your cellphone contracts is a nightmare but so is staying in one...what else am I suppose to do to resolve this?