The place to resolve this is
#2 .
#1 has nothing to do with this.
#3 is likely to back up
#2 .
#4 either won't work or if it does work, likely lands you on Enterprise's DNR. (Perhaps you don't care now, but you may do so sometime in the future).
Stay way from untrue assertions about "what we all know." While I certainly don't read the entire contract or even the entire series of cards which may be printed our or the like, but I do confirm that the rate and add-ons are correct. I can't speak to what "most people do" but I certainly suspect that many check the rate and yours would have been a lot higher than you expected.
You might get some sympathy if you simply say that you declined and the agent must have made a mistake (suggesting that you were conned makes you look foolish because the total number is something to be checked).
Make the call when you have time, are calm.