I am trying with the security group name now.
ALTER command says Line 1: Incorrect syntax near 'LOGIN'.
C:\>sqlcmd -E -d master
1> ALTER LOGIN [PBTF\Group - IT DB Admins] WITH DEFAULT_DATABASE = master
2> go
Msg 170, Level 15, State 1, Server THOTH, Line 1
Line 1: Incorrect syntax near 'LOGIN'.
1>
Any suggestions?