Date of purchase 2007y

stedman1 has provided you with accurate information.

You did not buy a new phone.

The "5" in the model number indicates that the phone has been remanufactured at a third party facility, possibly with non-genuine Apple parts.

So, you have a used iPhone 15 of unknown age with no warranty from Apple, although it is possible that the seller offered some kind of warranty with the phone. Check with the seller on that.

This would indicate that the unit has been refurbished by someone other than Apple. A warranty, if available, will be provided by the retailer.

Yes.

If you're unhappy about it, return it to wherever you got it and get your money back.