AIRTIME ADVANCE *****

I took an airtime advance of R110 for the first time in months, when i went back in it showed i owe vodacom an amount of R1600 and suddenly i had R1450 airtime on my phone. I have called Vodacom numerous times to escalated this as it's not even possible to take an advance of this amount and the only thing they tell me is "sorry you need to pay it back" how???? How can they just tell me i owe them R1600 and theres nothing i can do when i did not take and advance of this much and it's obviously a system error on their side!!!! Or can Vodacom just do whatever they want and hold people liable to pay? That's not how it works. I've been using vodacom for 15 years but the service and issues have gotten so much its pathetic honestly. I will now move to a different service provider that's not trying to ***** from people cause i cannot deal with this anymore. And Goodluck with finding the R1600 cause i will not pay for something i did not ask for or agree on.