Does an iphone Xr user (second hand) without origional purchase receipt is eligible to get benefits of warranty which is still valid?

Hi, hope this message finds you in good health, My iphone XR which I bought few

months ago from one of my known person is not catching sim card signals, I used

it so far with the same mobile carrier/sim card, it was working perfectly but

from last month it went wrong, Previously I talked with one of your agent , I

did exactly same things as the agent guided to make it work well, but it was

not successful, the agent took my postal address and suggested to visit the

apple store to change the device. Now before travelling to the apple store city

near me I want to make sure that apple store will handle the case without original

purchase receipt, since the person from whom i got this device said, he does not have origional purchase receipt, because it was a gift, he said, I believed the person, though I made a paper contract with him that from now on I am the owner of this phone. The iphone has valid warranty till

October 2020. Can you tell me now that apple store will handle this case

without receipt? and the answer i will get here is from apple agent or from any apple user? just want to make sure that the reply is authentic :)