So you paid $88.48 for a $59 phone and a $20 top-up card and taxes.
First off, that $20 airtime card is not refundable. (plus you used it up).
So you're left with $66.08 ($59 + tax).
At this point, who knows where the additional $25 reduction in your refund came from? No one has any idea who the gas station clerk was talking to. Plus the customer service rep you spoke to on the phone probably didn't have all the information (or probably didn't care). Who knows what condition you returned the phone and packaging in. Who knows?
If it was really that important to you, you should have waiting until the next business day to return the phone, unless you used the phone for a full 15 days (and 64 minutes of airtime) before deciding to return it.
Call PetroCanada customer service. I doubt they can do anything, but it's better than complaining here.
Maybe afterwards you can go to Future Shop, buy a printer, print out 1000 pages, and then return it after 30 days and expect a full refund?