Gumtree yet to respond to item ******

I was selling a guitar on gumtree.

I was approached by an Indian man with the username pillay, who messaged me and then swiftly called saying he wanted the guitar. I agreed for him to pay me and fetch the guitar. I received an sms with a Nedbank proof of payment, in my naivety - thinking that he had paid for the guitar, I handed it over to a supposed Taxify driver, I came to realise that the proof of payment was forged and I have had to cut the losses. However this man and his con friends have continued to harass me, threatening to come to my house if I don't pay them money. It is horrifyingly scary notion that something like this can happen. I haven't received a response from Gumtree in my attempt to report this name, who upon further research has been conning people. Something should be done about him and all of his 'business partners'