Transaction not reflecting

Money not reflected. Saturday a transaction was done by client (FNB) to our business account FNB. we were concerned that the money did not immediately reflect, 30mins later we called to ask whats happening and they told us about 12hrs, ask the client if there is a smart block. Monday, still no money in our account, the client sent us proof and called the bank and it said the money went out of their account. On our side still nothing has reflected its Thursday! Customer services keeps saying we must resolve with client. We are going together to the branch today! It is disgusting how money can be sent from on FNB client to another and it has not reflected, their was just the sunday and the holiday of 1 Jan, what could possibly be the reason!