Screen replacement might be under $200.
I believe your credit card warranty will only cover the cost (which you probably got at a discount on a 3 year) so they won't subsidize a new phone.
If there is no noticable physical damage, I'd take it back to the store and tell them it just crapped out. Bell corporate stores are not too bad. I had a similar problem with dropping a Blackberry. No noticable physical damage but I knew it didn't work because I dropped it. But they still replaced it under warranty.