Like I said: the device was managed by Engin. You cannot add it to the OBiTALK portal until and unless they delete it from their provisioning system. This is remotely managed/controlled by OBiTALK, which currently knows and identifies the device's hardware ID as being assigned to Engin, and it cannot be cracked, hacked or otherwise bypassed.
You can probably use the device without the portal features, as drgeoff described, by factory resetting it and logging in at the device's local IP address. To get the address, enter ***1 on the attached phone's keypad. The default login is admin/admin. You will have to disable remove provisioning, or it will likely be remotely provisioned to Engin again.