Vodacom altering my credit score?

I currently have a contract with Cell C ***). In early Jan, I asked to add a second contract onto my account (a sim only deal for R219). This was done very efficiently. The lady in the shop however, then forgot to load my sim swap request and i I was therefore without a phone that worked. After numerous visits back to the store and more and more promises, I decided after day 4 of waiting to cancel the contract and move to prepaid. This was completed - however I noticed a CONSIDERABLE difference in my signal quality. I am yet to receive a 4G signal on prepaid and often encounter edge (this finding is worrying I must say). I then decided to move back to a contract since I require a good signal. I went back to the store to activate the very same contract that had previously been accepted to be told it was declined. The reason: Poor payment on the existing line (impossible since this is on a debit order and a payment has never been missed)- as of a week ago Vodacom owed me R286. My credit score is extremely good too. I would like this to please be explained - has somebody done this on purpose? This is fairly urgent as the sim only deal expires tomorrow. Thanks