bad customer service

I'm not getting any assistance on money that was transferred to my fnb account from another fnb account but never cleared through to me they requested for proof of payments which the sender provided now they are telling me the sender should call their bank which she said she has done and they said the funds went through but ony end money never and still hasn't reflected in my account how can money just disappear in the air and the bank can't trace where the funds are and now I'm going back and forth without any money on my side