I bought a pre owned Iphone

Santi_0123 wrote:

Yes, and uh, it says that it's still under warranty until November, so, I'm allowed to use the warranty? until it expires?

Yes. iPhone Warranty is with the device, NOT the person. As long as it suggests warranty is valid until November, that's all you need.

Generally speaking a receipt is not required if it was purchased from Apple or an Apple Authorized Retailer. When Apple looks up the serial number of the product they’ll be able to see the complete history, including purchase date.

For example, there are many non-authorized sellers on Amazon and those products may be without a warranty or were/are sold with a third party (non-Apple) warranty.

Your phone should show its warranty status in Settings app (iPhone > Settings > About > scroll down to Limited Warranty and an expiration date will show.

Santi_0123 wrote:

even without having the receipts, box, or any other proof that I bought this Iphone? the old owner can't provide that as because she said she losts it somewhere

You don't need the receipt OR the box to claim warranty on an iPhone.

This is one of those cases where you won't really know until you try.

"Should be OK" is not quite the same as "Will be OK".

As a test, don't wait for a problem to occur. Take the phone in and ask for the battery to be tested.

See my answer above.