It's 08:30, their appointment window is 08:00 to 10:00. I'm here, they're not. I call the number on the account to make sure (it's early, someone might have overslept) and am told by the person on the phone that they will be here in 15 minutes.
If you can not BE HOME for the entirety of your appointment window then don't schedule the appointment in that window. We work seven days a week, surely there's one day that you can be home for a whole two hours. If there isn't then you obviously don't have enough time to use our service anyway.
*wait* *wait* *wait*