You’re here, which means the seller is likely gone, which means no refund and no original purchase receipts and no Activation Lock unlock. Which means you got scammed. You bought what is likely a lost or stolen iPhone.
The IMEI and the serial number will not allow remote tracking of this device, and are unrelated to removing Activation Lock.
We cannot help you bypass Activation Lock and access this device, and absent sufficient proof of purchase receipts from the original sale—which you undoubtedly lack, if this follows the usual pattern of fraudulent sales—Apple will not help.
You can contact eBay, though they likely won’t warranty this purchase. Same for reporting the fraudulent purchase to police, if that contact is an option for you. Which means you’re left to recycle this device. Yes, recycle. It’s not going to be useful to you.
The All Too Common SAD Reality of Buying a used iPad/iPhone - Apple Community
Oh, and one of the other scams is to sell an iPhone with no Activation Lock, but to get the IMEI blacklisted shortly after purchase, which means the seller reported it as stolen and pocketed your purchase payment and probably also collected a replacement iPhone, and the carrier is unlikely to remove the backlist. Which makes these iPhone purchases equally useless to the buyer.
