I report *****, now I am the *********?

Before this weekend I got a call from Asanda Enterprises expressing interest in an apartment I advertised on Gumtree. This guy was very eager to pay the deposit and 1st months rent, which all happened over the weekend. Then the next thing , they paid me twice and called me to request I must pay back the over-payment. I immediately realized that this is a ****, I read about it somewhere so I did not pay them back. On Sunday I started to receive verbal threats and texts with my address, photos of my front gate, telephone calls that tell me they know where to find me etc. So this morning I phoned FNB ***** line to tell them that there is a ********** account, these people are ********s . The lady on the FNB ***** line asks me what is my problem, I have in fact been paid twice and I must pay the money back to these **********. This is how much FNB cares about on line *****.