This question already has an answer here:
At level 6, Glamour bards gain the Mantle of Majesty feature (XGtE, p. 14):
At 6th level, you gain the ability to cloak yourself in a fey magic that makes others want to serve you. As a bonus action, you cast command, without expending a spell slot, and you take on an appearance of unearthly beauty for 1 minute or until your concentration ends (as if you were concentrating on a spell). During this time, you can cast command as a bonus action on each of your turns, without expending a spell slot.
However it doesn't really mention at what level you cast command at. Do you use it as a level 1 spell, or at the highest spell slot you can cast at your level?