Team names can be changed as long as the team has not played in a tournament during a season.  Once the team has played in a tournament, team name changes are not allowed.  

However, captains can form a new team with a new team name and pay the annual team organization fees.  That new team can then continue to play in future tournaments in the same season with different rosters.

Source:  Section 1.05 NAGVA Rules and Regulations.