Usha — Worst after sale service

My complaint #CC[protected] about Usha heater which stopped working in just 18 days is not being taken seriously. It's almost a week now. They say a part is not available. How come such a big company is not having the basic part 'a fan coupler' available? What is the use of after sale service then?
It's too cold nowadays and I am not able to use the heater just bcoz they don't have the part available. It will not be useful if they service it after winter season is over.
It looks my biggest mistake to trust Usha.