I think what the posters were saying is on the back of the confirmations you were sent in the Postal Mail (not email) it will state that the rates can be changed at any time and that right is reserved by Disney.
here is a copy of the back of the form they sent me for my trip. You may have to copy it and resize it larger as i don't want to break any guidelines as i don't post many photos.
So while what they printed on the FRONT may be what the CM said if they had any taxes increase or if the Computer wasn't able to add the charge for the 3rd person they may have added it. They aren't required to send a new confirmation if it was a charge that was to be added because it is the POLICY.
As others have said you need to call CRO or WDTC and just verify the amount that is either due or if its all set.
But its on your confirmation on the BACK where all the terms and conditions are printed in gray font that there is a addtional charge for any adult over 2.