Locked out of iPhone 7 Plus

Hello

my dad has an iphone and forgot his passcode so I was going to restore it for him but after reset I got the activation lock and of course he cant remember the password or apple id.

finally we manage to find it out and Im able to use it to login on icloud.com but when I use it on the activation lock it says that this apple id cant be used to unlock the phone.

what to do? Starting to worry I might as well throw it away...

local Apple partner says I have to send the phone to Apple, which will never be worth the hassle.

thanks in advance!