Poor service

Hello Peter, i went and sign a data sim card contract of R299.00 a month which is 30GB day and 30GB at night, which at the end i was supposed to pay R309 a month, with Vodacom. I asked the sales consaltant to please assure me that the monthly instalment will be R309.00 because i can not be able to pay more than that, for sure he assured me. That was on the 22nd of October 2020. Now comes deduction time on my account, on the 26th of October Vodacom debited my account with R181.02, on the 30th of November they debited R520.90, then i went and ask why they debited those two amounts they gave me a number to contact the finance department but there was no clear explaination. Then when i saw the December instalment which was R847.00 i went crazy. I still have a dispute of R520.90 and now they want to debit R847.00, unfirtunately i could nit let them debit so much money. I called their finance department again but they could not explain, they let me hold for ever for someone to assist me until i hanged up the phone. Then then i went to the shop the next day but still they could not resolve the issue instead when they check the balance on my account it was R1 573.98. Can you please help me Peter resolve this issue as soon as possible. Thank you in advance.