Flight changes.! What is the best way
 

Looking for advice for the future....

I've had to change a ticket yvr-mia-yvr,
The return flight was leaving at 7.30pm (March 11th) via yyz, overnight in yyz and then the 9.00am (March 12)to YVR.

My plans changed and i know needed to be back in YVR on the 11th, so i called SE desk to change the flight to the 10.55 am via yyz back at 5.30 yvr (11th)

Now my orignal tickey was a V class, confirmed upgrade both ways(j)....The change fee charged to do the above was $606.00CDN.!!

What did i do wrong?.

Thanks

This could just mean there's no V class inventory on the flight you're trying to change to so they gave you the next class (H maybe?) available. So you must pay the fare difference.