Why does my iPhone 15 show a 2007 purchase date on 'Apple Coverage'?

You bought a used / refurbished iPhone 15. It has no warranty coverage at all, so you are on the hook for any service or repairs.

If the seller told you the phone was "new", it might have looked new and was nicely shrink wrapped, but it was not new. With really good luck, the battery might have been replaced during the refurbishing process.

If you could provide the model number of the phone.......Settings > General > About > Model Number.......we might be able to tell you a little more about the phone. Please do NOT post the Serial Number for security reasons.

You might consider taking the phone back for a refund, or a really serious price adjustment, if you want to keep the phone.