ICLOUD

If the seller won't help, contact ebay; see the following: https://pages.ebay.com/ebay-money-back-guarantee/

There is no known way to bypass activation lock without the assistance of the previous owner.

If the phones were advertised as unlocked, contact eBay for steps to arrange a return/refund. Activation lock can not be bypassed.

Return them to ebay and demand a refund. There;s nothing to be done with iCloud locked devices unless you are the original owner and can prove it to Apple with the original proof of purchase from Apple or an authorized Apple Re-Seller. Ebay is neither.