Bad customer service

I received a call from Vodacom during December 2019 as my data contract was expiring soon. I advised the agent(name known) that I was not renewing my contract as I had found an alternate provider with a better and cheaper option. The agent requested that I give him a day to speak to management to match the offer from the alternate service provider. I agreed to Grant him the day to speak to management and he called me back later the same day with an offer of 20 gigs anytime data and a R65.00 airtime for R119.00 per month. My current contract was for R199.00 per month for 10 gigs day and 10 gigs night. I felt the deal was a good one and advised him to conclude the deal. He proceeded and processed the deal. End of January I received my old deal at the new price and my debit order was R375.00. On 10.02.2020 I lodged a complaint regarding the incorrect data I was receiving and spoke to an agent(name known) and she amended the contract to what we originally agreed to in December as they had listened to the call and assured me all was rectified. End of February I received 30 gigs of data and R65.00 airtime. I was under the impression that the extra 10 gigs was a gesture of good will for all my inconvenience. On 11.03.2020 I went onto the website for my wifi router and found that my debit order for end of March 2050id gonna be over R400.00. I phoned upgrades and the agent(name known) advised me that my contract was LL correct and that I should speak to accounts regarding my debit order. I phoned accounts and while speaking to them I was cut off on 3 occasions. I even asked the third agent if she will pse call me back if anything happens to the call. Still waiting to be called back. I need my debit order to be rectified before it's too late for end of March. At a total loss as to how to rectify the situation. This is not my first horrible encounter with Vodacom. The impression they give me is that a customer is a burden if we have a query. I hope to get the desired results as a matter of urgency.