Incorrect Billing

I have been a member of Sanlam reality for a while and my experience with them has been good when it comes to the benefits they offer but when it comes to billing me it has suddenly become a nightmare. Firstly the complaints department is non-operational on weekends and when you get through to the complaints department the agents don't have answers but a lot of assumptions to why I was dubble billed. I understand such technical errors do happen in businesses sometime but at least the business at fault should have a reason why it happened and not advise the customer that they should wait a period of 5-7 working days for a response as per Marlin the escalations manager I spoke to. I just want my funds returned ASAP, I don't want to cancel the membership due to their great benefits.