Su-Kam — home ups 1500va shiny, for replacement of transformer under 7 year guarantee

Dear sir
I bought a sukam invertor 1500va shiny in the month of june 2014. At that time this model comes with 7 year gurantee of transformer, this is also written on box when i purchase it.
Now about last week this not working. So i complained it to company. Company send engineer to check it. He found transformer is burnt. But he said you have to pay for replacement.
I complained customer care but they are providing proper resolution and close my comlaint without resolving my issue.
Kindly resolve my problem
.
I am providing following details:
Model: 1500va shiny, mfg date: may 2014
Serial no: 50503b[protected]
Puchase on : june2014
Complaint no. 27944c13080918 date 8sep2018