I paid for a service that led to the destruction of my vehicles gearbox

Really disappointed in the sloppy workmanship that led to the destruction of my Mahindra Bolero gearbox and the refusal of Raceview motors to accept any responsibility. After the 20000km service where they replaced the gearbox oil,the lower drain plug was not tightened properly causing it to work its way loose, fall off, and the oil leaked out of the gearbox. The gearbox then seized on the highway at 10pm Graham Ramsdem, the workshop manager was the only individual who bothered to communicate with me and although I sent an email to the Dealer Principal, Celia Ries, she has totally ignored it and refused to reply. Totally disgusted with your handling of this matter.