Disable activation lock in iMac

How can I disable or remove the activation lock without the initial imac owner? The situation is that we have multiple imacs in one room, and most of the imac is locked due to the person sitting in the device is logged in with their apple id, and now we can't format the imac

Is there a way to contact apple support via email, also, the country is not included in apple support or in this situation where should I contact first?