If you have an Interaction number then they would honor that usually or at the very least try to make it up to you by giving you other offers like credit etc. But from my experience if you had the Interaction # and you keep persisting, they would have not much choice but to honor it however you would have to speak with a manager in customer relations/retentions. Customer reps can't help you there. If you don't have an interaction # and you only have "verbal" agreement then there is no proof of that deal being offered, even a message doesn't really count. You really need an Interaction # to have a strong argument. Next time if you didnt get an interaction #, make sure you get the person offering you this deal to make notes under your account and have them give you that interaction #.
I kept my old 6gig plan and not pay a single penny more because someone messed up on their end and I had that interaction # to back it up.
You could dial *611 from your Rogers cellphone and it'll connect you to Rogers. Get into mobile sales/customer care. I wouldn't waste your time with the people in that department, just ask to be transferred to customer relations. If they persist that they themselves can help you, just be firm about wanting to speak with someone from the customer relations department. Once you're there, explain your situation with your IT # and see what they say, my first guess would be them apologizing and try not to honor it (this is normal). Just stay calm but firm about your argument and see what happens. Good luck.