"tried to make an appointment..."

Tried to make an appointment today as experiencing some abdominal pain. Followed the instructions on the website and phone. In fairness my phone call was answered first time and reasonably quickly. Spoke to a receptionist who, as it was after 15:30, told me that because my need was non-urgent I need to call again tomorrow. Before 15:30 of course...

For the life of me I do not understand why I need to do this. It seems that in 2018 it is beyond the ken of at least this medical centre to manage a list of patients who their clinicians need to speak to.

No where on the web site can I see reference to this arbitrary cut-off time of 15:30. Am I left with any confidence that if I do call tomorrow they will call me back...