***** on my vodacom account

Last year in a December I discovered that someone had committed ***** on my vodacom account, I learnt this when I called Vodacom to enquire about my sim which seemed to be blocked. I was then requested to send an email to ***** dispute department at Vodacom to which I did not receive any response other than a reference number. I contacted hello peter for assistance, a day after contacting hello peter vodacom sent me an email apologising for not responding to my query. They asked me to send documents that I have sent initially with my first query, which I did, this was in December 2017. I never heard from vodacom again despite numerous attempts for them to solve this case. Yesterday, 16 September 2018, I received a letter of demand to which vodacom says I owe them R20 645.59.

This baffles me as vodacom is aware of my matter and promised to resolve it. I'm appaled that now I have to pay for a phone I know nothing about.

Please help I don't know what to do anymore.