Unauthorized deduction on account

On 21st July I received a message saying a high usage was found on my phone and is now locked. I need to pay an amount of R 3,687.38. So I phoned and then was informed I must pay over R 12,000. Needless to say I was shocked as I do not use my phone that much. I worked through the day and use the company's wi-fi. I app**** for a loan from my bank because I do not have this amount of money. ON the 3rd of August 2015 my phone was soft-locked again. I paid over R 4000 again. by the end of August I went into Vodacom Savannah Mall and a query was booked as the outstanding money was deducted from my bank account . A refund was made in October of R 6,000. At he end of October i received a mms indicating an outstanding balance on my account . I do not owe Vodacom any money nor did they contacted me in to tell me that they are deducting the money. I have paid over R 13,000 for charges i did not made. Vodacom has contacted me and changed my contract in the beginning of August to a R 110 per month contract. I did not request, discussed the change prior with them. Now they changed their minds after they made an agreement with me to pay me 50% back by deducting it on a monthly basis R 810.