I tried to book a telephone appointment via their online booking portal.
"There are no evening appointments available on the date and time required" so I have to call their number.

The mind seriously boggles as to how, in the 21st century, they could overcomplicate this. Why is booking any type of appointment a sadistic back-and-forth exercise?

If I call, I expect it to go something like this:
- What time would you like the appointment?
- 123
- And what day?
- MWHAHAHAHAHAHHAHAHAHA Nope! We're only open on XYZ at 789!
- ... Then... I'll take... XYZ at 789...?
- Ok great!