Trai — service centre had not done his work fully

Address:

Samastipur, Bihar, 848101

Sir /madam
I have purchased a redmi 6 three months ago but it's has been hanging after few days so i submitted the mobile phone in to mi service centre samastipur. He told me it's display issue he ask me give some time after 7days he called me. I will receive my cell phone but i can't check another issue. My cell phone setting had changed as like before submitted mobile the fingerprint scanner is ok but recently i can try to use fingerprint lock setting but it's not available. Than i will go to service centre again but he didn't respond.
Thinking you