You should bloody well be able to speak to one.
I got a letter for a follow up medical appointment. When I was at my initial appointment I was asked if there was any time I couldn't do - I told them and, of course, I've been given an appointment when we're away.
The letter says to ring and let them know. I've been trying for the past month. Different times of day, more than once a day EVERY FUCKING DAY. Ive called direct, I've called reception and asked to be put through and it rings and rings. Never any facility to leave a message
Then you get to the snotty bit of the letter that says "if you're not able to attend the appointment and don't let us know you'll be returned to the care of your GP"
How the fuck can I let them know if no-one answers the fucking phone.