Through this email, I would like to inform you that my name is ____________ (name) and I am a resident of _____________(mention address).
This email is in reference to the purchase made for ____________ product (product details) against invoice number ___________ (bill/invoice number). I am enclosing the invoice with this letter for your reference. I formally request you to extend the warranty period for ____ more (months/years). It would be really appreciated if you could share details/procedure and quotation for the same.
Thank you for your time and support. Looking forward to hearing from you soon.
_____________ (Contact details)