The advice provided by the lawyers should be part of the records of the scheme so, if you are an owner, you are entitled to see it. If they say it was verbal, then you are definitely entitled to challenge it. Mediation is definitely the way to go.
By the way, I can’t believe that any competent strata lawyer would advise strata managers to ignore the law, which states that all owners in a scheme are entitled to so I would take this second-hand advice with a large pinch of salt.
That said, I’m not sure if you are an owner in the scheme to which you are referring. If not, different criteria apply.