FNB slow services

Debit on my account since 6 October 2020. The merchant has corrected the error and didn't deduct any double monies further. I since raise this 4 and 3 weeks back with FNB, first telling me it's not them but the other company, of which I got references from them that they have stopped everything and the problem is now with FNB holding my monies, I did a dispute 10 days back of which no response. I really want my monies if it was the other way around they would have constantly called and sent letters.