Vodacom forged my signature to avoid taking responsibility

I handed in my contract phone for repairs at the Vodacom shop in Zevenwacht mall on 17 January 2018 and I still have not received it back. When I went to fetch it I found scratches that were not there before, which I disputed. I was asked to write my dispute down and submit to them for investigation. When I did an enquiry a week later I discovered that they forged my signature claiming I had signed it in with scratches. The documents they gave me had my original signature and the forged signature. I refused to take it back, showed them the discrepancy and they again said they would investigate. Needless to say I still have no phone 2 months later and their response is "the matter is being investigated". No apology or accepting responsibility from Vodacom and they are still deducting my money (twice already) even though I do not have a phone.