But the FTC rule does not apply:
The FTC's Telemarketing Sales Rule requires telemarketers to make certain disclosures and prohibits them from lying. It gives you the power to stop telemarketing calls you don't want and gives state law enforcement officers the authority to prosecute fraudulent telemarketers who operate across state lines.
There is no federal law that regulates the cancellation of telephone agreements. Though there are certain state and local laws that require telemarketers to provide a cancellation period, don't agree to buy on the assumption that you can cancel later.