When I checked my balance in mobile web on my cell phone it said it was $900 something. I asked my friend about it and they said that when they check their balance its never that high on the bill, so the plan probably isn't included in the price.

Does anyone know for sure?

because you have mobil web and not v cast you are using your minutes and could be liable for this $900 bill. Sorry about this and the retail person never told you. Call Customer Service today and tell them no one told you when you ordered the phone and you may get a credit. Be real polite. They call it a rework. i used to work there and some people got it, and nasty people had to pay the bill.
Sorry again.