False Promise to retain customers and bad management service

At the beginning of December 2021 I contacted Rain Internet Provider to cancel my 4G contract because of connection issues, the sales agent who helped me convince me to upgrade to 5G and was told that i will only pay pro rata In December on the 4G sim and not pay for the 5G for the month of December and that i will start paying for the 5G in January 2021. On the 30 December 2021 a debit order of R495.00 went through my account and i then immediately call Rain to query it, and the manager told that the agent was wrong , she was not suppose to have told me that i wont pay for the usage on the 5G For December. She also told me that she will listen to the tapes and get back to me on Monday the 3 Jan 2021, today is the 07 Jan and still no one has called me back. Is it ok that i have to pay for the mistakes of their Agent, I am so disappointed, this is not he kind of service i expected from such a big company like Rain.