Why does my voice agent offer times in the wrong time zone, or ask which appointment length I want?

The times the agent offers come from the bookable service (calendar) it is connected to. Edit that bookable service and set its time zone there (for example Mountain time), and the agent will speak the available times in that time zone.

If the service has several duration options, such as 30 and 60 minutes, the agent asks the caller which one they want. Remove the options you do not want so the agent only has one.