A polite note telling them that you can’t re-set the AGM but they are welcome to come along, vote and nominate for the committee, once they are registered on the strata roll.
You might also gently suggest that they take a slightly less aggressive stance when dealing with their neighbours which will stand them in good stead now and in the future, especially since, by their own admnission, they don’t yet know how things work in your block.
You have followed the rules and you suggest they acquaint themselves with the basics of strata living through the handbook supplied free by Fair Trading before making demands.
Meanwhile you look forward to their contribution to the continued smooth running of what is a happy building.