FNB ***** department requesting documents that seem to be be obtainable

I was ****med out of a large sum of money via fnb, a matter I immediately reported. This was done via a sim swop. Fnb declined to return my funds because they claim no proof of sim swop was provided. The first I heard of this required proof was 2 weeks after calling daily to follow up. Once I was informed of this I went to an mtn branch and got proof of this sim swop. However fnb said they needed proof from mtn forensic department, which everyone I've spoken to at mtn insists doesn't exist. The FNB ***** team gave me an email to follow up to and mtn have given zero reponse. Hence my complains agains fnb, african bank (who gave my details to the ********) and mtn who have all proved entirely dispassionate about solving my problem.