Ok, there's some errors in this.
Yes, if the hardware upgrade policy changed, then yes, it affects you. Partial rebate is at 18 months, full rebate at 24 months. The rep told you that you were eligible on November 21st. He didn't lie, you are, just not for the full rebate. Perhaps a miscommunication on his part.
Contracts lock in your rate plan. It CANNOT be changed during your contract term, notice or no notice, they simply can't. Features, such as Caller ID, voicemail, etc, can be changed on you, as well as the system access fee and e911 fee, provided they give you 30 days written or verbal notice (usually it's a letter or bill insert). Once you are off contract, they can change your base plan on you, again they must give you 30 days notice.