MTN - Incorrect provisioning but charging me full price every month

I have taken up a black Friday promotion data contract in November 2018. I have been getting the correct amount right up until April 2020. My night data is half as opposed to what i should be getting. I have done the upgrade via telephone. MTN refuses to amend as they want me to provide proof of why i should be getting the data that i state. Should they not have this? After all the running around I have contacted MTN direct who did the upgrade and they refuse to provide me with the proof needed to have MTN support provision my contract correctly - Voice recording. Why should i be running around to get this? why cant MTN Direct provide MTN Support the recording? This issue has been outstanding since April. MTN refuses to keep me updated on anything. Every consultant passes it over the next department. No one wants to take accountability in assisting to resolve my query. I have never received such bad service in my life. Really pathetic from MTN. I regret having my 2 contracts with them.