Microtek International — Basic required documents for repair of inverter within warranty period

Address:

Vill Maldahiya PO Siswa Bazar PS Paharpur Motihari East Champaran Bihar pin 845422

We have raised a complaint regarding charger is not working in my inverter which is guarantee period. I have given bills to service engineer and they are asking for manual of the inverter. Is it correct required documents for availablement of guarantee. If yes, kindly suggest me all documents for warranty??? And also provide the service charge for visiting a engineer. They asking for Rs. 350/- for visit.