Backdating Agency Agreements

Has anyone had the issue of a strata manager backdating the agency agreement, for example from the 30th july back to 30 june.  Can anyone tell me if this legal?  Also is it legal to be coerced into signing an agency agreement?  I was informed by dept of fair trading that even though a motion to change strata managers owners weren’t under a legal obligation to sign with the chosen manager and could sign with another manager.  Is this correct? What is enough time given in regards to a letter being sent to inform owners of meetings?  I was told about clear days and that at least 14 days notice should be given, is this correct? Thank you