VMS Help TELNET, Qualifiers, /UNBIND_SESSION  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /UNBIND_SESSION network_device terminal_device

    Optional.

    Unbinds a network device (BGx:) from a TELNET terminal device
    (TNAx:) that was initially bound by a BIND_SESSION command or
    qualifier.