TELCOM PLIZ SOLVE MY ISSUE

I took a contract with telcom.A lockdown promotion home wifi for R399 a month in August 2020 September l was billed R1200. I went up and down trying to solve the problem calling different numbers no one was interested in solving my problem l end up paying that amount next month they continue overchanging until l had to fight again at the end they said it was their mistake now its solved they owe me the balance of 800 October November they charge me my normal bill December they again Charge me R1200 yet they said the matter is solved now lm trying again to solve issue lm being told to call different numbers all of them they say its not their department they cant solve it confused l dont know who will solve my problem they say l owe 2000 yet l never missed my payment.Hello Peter pliz help.my landline number is ***.