I'd agree that the practice of running the charge before getting the service is at least questionable, yet I know hotels, tickets for shows (picked up at will call), some restaurants, and others do it as well.
Not sure why it matters if the call gets done on the first day or has to be rescheduled. Either way, they're charging for the service before it's actually performed.
I assume if it never gets done, or if you change your mind, they will issue a credit to your card. That said, I honestly don't remember what my CSR said in that regard. She was reading from a script and I probably was only half-listening.
Not that its OK, just that its done elsewhere. I struggle with the concept, but pony up if I really want something. Since Whole Home DVR service installations typically involve a fair amount of hardware at a discounted price...I guess I could live with it in that situation.