Problems with Cambodian Birth Certificates

I am trying to get a visa for my wife's sister to come visit us in Australia, but her Birth certificate has a different date of birth for her father than their family book.  Visa company here say everything has to match, but commune are saying they can't change to match all family book and dads birth certificate and we need to go to court to get permission which would cost thousands.  Please help if you have any solutions.

You either have the fmily booked or the birth cert amended.  I would assume amending a birth cert is the easiest option.  I'm sure it can be done with say $20 as pocket money.