Faber — cooktop

I have purchased a cooktop on 08/01/2020 from the exibition, after installation on the 2nd day the flame goes off when you put it on low gas, i complained & an engineer came & told me that since this is a new model he was not aware of the technicalities & senior technician willcome to look at this complain within 48 hours, it has been so many days now & no one has come, we have tried calling the the customer care but it is impossible to get through to them.
It is very disappointing that a company like faber should have such a horrible after sales, imagine buying a nnew cook top & not being able to use it within 2 days of installation, dont you`ll have experienced engineers.
Kindly do the needful as soon as possible since i have discarded my old cook top & cannot carryout slw cooking on this one