dislpay of unit switches off whilest in use

my sansui tv 55 FHD LED i submitted in 11 December 2015 for assessment as it was displaying but switches off whilest in use and only sound then on the 18 January 2016 i collected the unit and asked that if the tv give me same problem,what should i do as i stay far away from PE about 130 Kms adn they say i should bring it back. TTS company who asssess the unit found no fault tested but today the unit suprisely do the some problem of display switches off whilest in use and only sound. i paid for car hire 1000 to submitt and to pick it up from PE to Grahamstown. i even asked them to pay back my extended warranty because travelling from Grahamstown to PE and return its costing me too much and hifi corp doesn't seems to care about that. please assist me on this regard cuz i asked them to give me a new unit or my money back but they refuse to do so