What if the Activation Lock can’t be open because you do not have contact with them?

No one here including Apple can help you remove the Activation Lock. It is a security feature against data retrieval if an iPhone is lost or stolen. You will need the previous owner's information to remove the Activation Lock. There is no way around this.

Axel F.

Without the Apple ID and Password of the original owner, you will never be able to use the device. If you can't get your money back, recycle it at the nearest Apple store. More information...

Turn off Activation Lock - Apple Support

Activation Lock for iPhone, iPad, and iPod touch - Apple Support

Recycle the useless device.