Warranty rejected because of incomplete service

Took my Haval H6 for 75000km service, thinking these guys will do all that needs to be done. How wrong was I!! They were supposed to have changed the gearbox oil on thus service as per my service book.My gearbox started jerking at gear change, took it to Haval which said my gearbox needs to be replaced. Thinking warranty would cover it I wasn't worried, until I received the phone call today to say it's been rejected because Steve's Auto Clinic didn't replace the oil!! These guys get their service schedules from who knows where, definitely not the correct places!! If you value your warranty, don't use these guys!!