waiting for proof of payment from ***

This people claim that they paid money into my Acc on 17/07/2015. now i asked them to give me proof of payment,they fail to produce one. i have been waiting since 24thJuly to get that proof. they keep telling me about IT department. I went to their branch,i call in every 2 days or so and i send emails but no one seems to care or have answers for me.how long will it take IT deparment to trace that payment? I am now confused and frustrated by this people ((Tsholofelo,Shaldon,Ivan,Bevely,Sylvia,Marissa) because i spoke to all of them an they keep saying they wil get back to me and never did. i dont know what to do anymore please help