Bad brand laptop contract

I am extremely disappointed !!! I took out a contract with vodacom for a Mecer Guru laptop. It has been giving me so much hassles whereby the laptop will randomly start displaying either a full/partial black screen while typing and it also recently starting shutting down randomly when not plugged it. It then takes endless attempt to turn back on and struggles to charge thereafter. Why would vodacom even sell a brand that simply does not work ??! I have multiple contracts with vodacom and this is the treatment I receive. It is very disappointing. Am I expected to continue paying a laptop contract with a laptop that does not work ??!!