Unregistered (VOLO) phones can use Virtual Office login feature to log in to another phone. A VOLO phone user can press the appropriate key to request the phone to register again to its TN and continue to work as a regular Unistim phone.
However, DVLA phones are not designed to make calls similar to that of a normal phone. They can only be used to VO login to other phones. Also, emergency calls can be made from DVLA phones.
