Whirlpool India — Bill misplaced and need to replace washing machine motor under warranty

Hello

please i have purchased fully automatic top load washing machine in nov 2015 and my motor is not working which is still under warranty.
model no -31104
serial number-INF[protected]

service technician visited and charged rs 470 for visit charge and did not changed motor because of invoice not provided.

please raise the issue and provide me duplixate bill