Faber — Complaining about four burner stove repair

Hi team, I got my faber hob 4 burner repaired (bought in sept 2021) yesterday as one of the burners wasn’t working. Gas wasn’t passing through. The guy said he had to change something in each burner and has billed me 8500/-. I was told I’ll get the receipt on WhatsApp but never received any. When I called toll free number I was told that I was cheated. I had called the same toll free number to request service and was assigned a guy. I’m not sure what’s happening here. Can someone help me please? Thank you