"Orthodontist department"

I am unable to get through to this department as the telephone number on the appointment letter does not work, I rang it 70 times yesterday thoughout the day. Rings for a while and then stops. This is the same issue as the other writer 2 years ago. Is there still an issue with the phone lines. My daughter had a mould made in October and was to get an appointment this week to have it fitted. However, I received an appointment letter 4.11.19 with an appointment date of 01.11.19, which was the next day after her initial appointment. How do I change this appointment. This is really infuriating.