"Not allowed to deal with my child's appointment"

Got a call from oral hygiene about my child, asking to speak to them. I wasn't sure who it was -  they confirmed it was the Altnagelvin hospital. I explained to them that they were a teenager and I was their father to which I was told they didn't have to speak me.  I replied that I dealt with my child's appointments as I assist them to all appointments and can I not deal with the caller? They disagreed with me.  I queried why why they would be looking for a child at 2:30 in the afternoon when they would be in school.

The caller raised their voice and asked why I being cheeky. I tried to explain that I was the best contact for making an appointment. They asked me to get my child to ring the doctor  I asked for a phone number, but the reply was that they should ring the hospital and hung up. 

I felt like I I wasn't allow to deal with my child's affairs  and it left me feeling embarrassed . I went to the out patient's  to complain and the staff were fantastic.