****ed Off with Telkom

I have a contract with Telkom, in the 21st month which was May 2019 i received a call that there is a May special and i can upgrade, i was told of the May special. I was so very excited and upgraded there and then, on the debit order day there was a huge amount deducted on my account, queried with the branch and i was told that i was due for an upgrade and the person who helped me migrated me by mistake, the guy escalated the call, i received a call and the guy i spoke to told me that there is nothing he can do, money was deducted in my account and i want it back