I want my money back from telkom that they owe me and their rude consultants

I want to report telkom the glen mall, l had a contract with telkom it ended November last year 2020,just before the end of my contract telkom send me statement that lm owing them double the amount l was paying monthly, it was a contract phone l was paying 350 per month, amd when they sent that statement l had to pay 700 that month l did pay. Now after the contract ended and l closed the contract with them they sent me a statement that they overcharges. I went to the glen telkom shop one of the rude consultants told me telkom is owing me that money they going to refund me they logged a ticket with their billing accounts department and that lady even gave me a case number. And told me they will call you after an hours. L waited for their call and the following month of which it was February l went and do a follow up that lady was rude to me telling me the is nothing they can assist me with and told me to wait. Im still waiting now it April no one has contacted me regarding my refund lm so hurt that is my money l worked for it so hard for them to treat me like that. Telkom that is near clicks sife the glen bad service