MTN horrible service and I'm charged for it!

MTN was hounding me to upgrade or change my contract. So, stupidly i took their call from *** on 15/09/2022 at 16:07 and spoke for 7 minutes. The guy on the line told me since i didn't want to upgrade or get a new device, he had a deal that would save me roughly R70 pm. I asked repeatedly - I don't want any additional charges he confirmed. Come debit order date and i am billed R161.00 MORE than i have been paying all along! This was not was agreed upon! Why would i agree to pay more when it was advised ill pay less. I have since reversed that debit order and paid MTN manually the correct agreed upon amount. (actually ive paid my old premium - so technically you should ow me) When i sent a query to MTN i was told its a pro-rata amount? I never agreed to any such. If its an issue - rather change my contract back to what it was. I refuse to pay any extra fees because of your errors. Please fix my ***