Originally Posted by YEG USER

This happens from time to time. When you made your same day change at the airport the agent accidentally put you into a Tango fare bucket instead of a Tango Plus.

You'll need to contact Aeroplan and provide details of the fare you actually purchased. They should be able to give you the proper mileage credit.

EDIT - Something doesn't add up with your story, I missed that you flew home a day early so this wouldn't count as a sameday change. If you did change your travel date, you might have been charged a $50 change fee plus $25 in fare difference and actually changed your ticket to a Tango fare. If this was the case you will be out of luck as the system would show that you purchased a Tango fare. This is one of those cases where you need to double check what the agent did when changing your ticket.