Debit without authorization and debit mandate

I enquired about the debt counseling service they offer and was interested initially but then told the person I am no longer interested and even sent him a whatsapp as he sent me documents to sign which I never did. I agreed to the R595 to be debited and that's it. They now debited my account with R2595 and I am out of pocket. It's been 2 weeks that I am trying to get my money back and no one gets back to me. It's am very disappointed that a law firm trades like this. I want my R2000 refunded and mandate for debit to be removed immediately.