Struggling to have defecfive item replaced

I purchased an 8 channel camera through of which one of the ports and one camera was not working. I logged a return and subsequently returned the defective parts.

I was then informed that they require the entire 'set' that was purchased. Clearly I was not happy about this, indicating that because I was supp**** a defective product, I mist now carry the cost of the call-out by the technician again, and then pay another fee for installation (again) when supp**** with the (hopefully working) replacement. None the less I returned 'the set'.

To my dismay I was contacted by Tamara M, indicating that (again) they did not receive the entire 'set', and I was return (the already returned) hard drive and camera. I referred her to previous correspence, urging her to contact her colleague who already received the parts in question. Upon which I received this reply: "Please provide details of the items was packed when returned" Really? She still could not contact the agent in question who ALREADY RECEIVED it finalise my return? How is this treating a customer fairly when I was supp**** a defective product, do not have use of a product I already paid for, and have to incur extra cost for re-installtion fees because of the defective product I was supp**** in the first instance. Then to top it, the agent can't even conclude the return of 'the set'!