Unresolved dispute

I've been struggling with Vodacom to get my account up to date, due to incorrect billing and changes to me packages I knew nothing about. Last year in May, I went to Istore in Menlyn for a Topup contract for a 13 inch Macbook. Everything went well, got my book & went home. Suddenly in Nov, I recieved an invoice that I owe +-R3000, and knowing I pay around R1400 every month. I called Vodacom & was told that this is due to an Open line contract. I immediately logged a dispute and stopped all debit orders. The arrears amount was refunded, and all was well for two months. Then the open line bug hit me again, and after numerous calls & e-mails, my issue is still not resolved. The call centre agents are all seeing one thing, the arrears on my account. Thinking that was enough, end of Jan this year, I got a call to upgrade three of my contracts, and was given discounts which I gladly took. To my suprise one of the contracts was made an open line. This is a data contract used by my 13 year old son, and he made calls on that line unknowignly. This was not discussed with me at the point of sale, then I was clapped again with a R5000 bill. I disputed again & now I still owe them around R1800 which cannot be explained how it came about. Finally I thought I spoke to someone who understood what I'm talking about, and he promised to request the back office to refund the amount within 7 business days. Two weeks passed & I decided to follow-up again, then he responded via mail to say he apologises for the misinformation, the refund was done in Dec 2018. The question now is, if the refund was done, why am I still getting high bills, threatening calls and irritating texts. I'm tired of getting IVR calls & sms threatening to suspend my lines. I need Vodacom to own up to their mistakes & clear my name and account, as this has already affected by credit profile.