Did not fullfill their promise

I mistakenly sent cash to a wrong number, I went to gateway branch to log a case on the 18th of Dec 2018, they promised to reverse the cash within 7 working days, a week passed without any communication, i went to another branch in Durban they told me they are still investigating, then they sent me a message saying they can"t reverse my money since the other party is not answering the calls....