It sounds like you have every right to feel how you feel, but by saying it's a drop in the bucket for a company like Verizon you clearly realize that they are a big company so you must realize they cover their backside.
While a Verizon rep clearly had no idea what they were talking about by verbally telling you that you qualified for the credit, I have no doubt that somewhere in all the paperwork you signed there is either nothing mentioned about the credit or if there is it clearly states that you must sign up for a certain plan with a certain number of lines and with a certain type of phone etc.
I watch People's Court enough to know that a verbal contract rarely has any value, especially if the other side clearly disagrees.
If you got a basic phone and a 2 year contract that means you could have paid as little as .99 cents for the phone; Verizon is too smart to give you a profit of $149.01 by purchasing a less expensive plan and a much less expensive phone.
It's great of you to share your experience though and I wish that everyone would research deals such as these; if it sounds too good to be true, it probably is.