Upgrading Miles Plus Money Ticket

Hi there
Hoping someone out there has done this before and may be able to help?
I'm having a little pain dealing with VS to upgrade a Y miles plus money fare I have booked for SYD-HKG return. I've called their Sydney office who advised I would have to pay a $100 'reissue' fee plus the difference in fare and points.
When I look at the MPM T&Cs it states that no 'Change' fees are applicable when buying up to a higher revenue class.
So I'm wondering, is a 'change' fee the same as a 'reissue fee in this instance?
I've tried calling the UK office and was told no 'change' fee was due but was then given 3 different figures to upgrade!
Thank you!
Hoping someone out there has done this before and may be able to help?
I'm having a little pain dealing with VS to upgrade a Y miles plus money fare I have booked for SYD-HKG return. I've called their Sydney office who advised I would have to pay a $100 'reissue' fee plus the difference in fare and points.
When I look at the MPM T&Cs it states that no 'Change' fees are applicable when buying up to a higher revenue class.
So I'm wondering, is a 'change' fee the same as a 'reissue fee in this instance?
I've tried calling the UK office and was told no 'change' fee was due but was then given 3 different figures to upgrade!
Thank you!