roaming charges

Before leaving for Mexico I spoke with a rogers rep so that I would not end up with a big bill. I bought their text package and was diligent about making sure my ipad and phone were either off or in airplane mode and I still ended up with a $600 bill. When I tried to dispute this all I could get from them was an offer for a payment plan. Great! How can you get a bill that large from checking a couple of emails.