Bad service delivery ,poor communication

We have a Haval Jolion ,key was not synching with the car and tried to book s slot with a branch as the car.We were informed that we had to go threbranch where we bought the car, which we didn’t want to do as our previous dealing with them were absolutely challenging.Was told the diagnostic cable was needed to reset the key ad engine light was on on the deskboard.My husband decided to book the car for a service as well at that point as it was close to the next one.Any case service was done ,but the alert never disappeared.Phones the branch to informed them,was then notified that their cable was not working meaning the cable was never connected when our car was serviced.Long story short,our warranty with Traffic was nearing the end and my husband extended it.So we were given another day to bring the car in,to see why the engine light is still on.At this point we are all on edge as there is no resolution.warranty was never renewed no one takes responsibility,when we phoned to confirm the booking,so we have a car that can blow a gasket at any stage.Nothing is working on the deskboard accept the radio.Please assist