Expensive Phone Bill

Well lucky for me, my phone bill wasnt the normal $80.00 it was $450.00!!!!! I wanted to freak out. I went to Mexico in August and my phone was supposidly on "international mode" but really it wasnt. So i was using my phone away not realizing each text was costing me .50 cents per text. Thinking i was in the clear of a not so expensive phone bill, i recieved my first bill. It was 100.00 i said okay, few extra dollars for minutes. Then i get my next bill 2 days ago, and its $450.00. I was very very very unhappy! So i called verizon right up flipped out, because i thought my phone bill was international to find out it was never changed over. So after all that i got a $100.00 credit and i still owe verizon $350.00! DONT use your cells out of the US they will rob you!