A:
Maybe yes, but the answer is NO if you don't have internet service(or the cabling used to provide internet) to your house... What they're not telling you is that they're using voice over IP, which is phone calls over the internet. "Voice over Internet Protocol (VoIP) is a technology that allows you to make telephone calls using an internet (or private network) connection typically over a broadband connection instead of your standard phone line."
The media company should know if they can provide this service to you(Voice over IP). If so, then you should be able to use any router of your choosing, and purchasing one is cheaper in the long run.
The reason that they can provide phone service so cheaply is that by using the internet connection, they avoid Federal line charges, fees and taxes for phone lines.
The drawback is that your phone will now operate over the internet, so if you lose power, then it will not work like a standard, wall connected landline that draws power from the phone line itself.