Unlink apple id

Apparently you acquired your device second hand from someone other than Apple or an authorized Apple reseller. The quote below explain what has happened. You apparently didn't know to heed the advice given below.

"Before you ... [acquire] an iPhone, iPad, or iPod touch from someone other than Apple or an authorized Apple reseller, make sure that the device is erased and no longer linked to the previous owner’s account. "

 What all this means is that there is no way we can help you. We are not authorized to remove the activation lock from any device. And, under your circumstances, Apple will not help you since you cannot provide proof of ownership that Apple will consider to be sufficient. You would need and have your purchase receipt for the device from an authorized Apple seller with the device's serial number on it. 

All I can suggest is that you try to recovery the needed password (or possibly the purchase price) from the party you acquired the iPhone from. Recovering the password is the only way the phone can be made functional for your use. And getting it from the person you acquired it from is the only way to so.

You can try iCloud.com/Find My Phone using a computer browser and remove the phone from your account.

Find My Phone – Remove device.