You'd only pay the pro-rated amount of using the service for the first 15 days, presuming you cancel the 1st day after the 14-day grace period.
But yes, there are likely other charges to crop up over and above the $200 + ETF you'd think you'd be paying. Like the activation fee, taxes, and partial-month's service.
Ah, true. In California we have a 30 day grace period, which would mean paying for a full month.