Legit use of pending erase

I recently purchased an iPhone 5S from a seller on Ebay. When the device arrived, it was wiped but activation locked and still associated with his account so I sent him instructions on how to erase and remove it from his account. I tried the hard reset and upgraded the iOS, but same activation lock message appeared.

The seller successfully was able to erase (via Find iPhone), but according to him, it still says Pending Erase on his end so he cannot remove the phone he sold to me from his account. I have the phone connected via WiFi to the internet and it has been all along.

Any suggestions on what I should do? Should he call Apple or is there anything else he can do?

Thanks!