Verizon should have helped you more. I just had this happen to me as well and Qwest was more helpful than Verizon. Qwest said this was another case of "slamming" and they have a process of working with the PUC (Public Utilities Commission). Qwest removed the charges and they said they'd deal with the fraud complaint. It happens often enough that they have a system in place to deal with this. Verizon should as well.

I think you should contact Verizon again, let them know what you found out, and find out if there's any kind of a block you can put on your account so this can't happen again.

Good for you for being vigilant! Imagine if you hadn't opened your statement and just let automatic payments take care of it for you!