No response on onsite warranty

I purchased an Acer Aspire E5-771 from Mustek Durban on 10/02/2015.<br> <br> Within two months the screen started turning off, turning grey or flickering. I reported this Laptop fault, on the 10th, 13th & 15th of April. A Technician came on the 16th April and said he re-seated the connection to the screen, within a few days it was back to the same.<br> I reported it again on the 28th of April and 11th of May. The laptop screen is continually going grey or getting colored lines. <br> <br> I purchased a upgrade of the warranty to 3yr onsite. It is almost impossible to work on it and I am getting no help from the warranties department.<br>