"Impossible to change an appointment"

The system for contacting Outpatient Appointments is increasingly difficult. I emailed to reschedule a full week before my appointment and the automatic reply said they'd get back to me within 48 hours, but my appointment is tomorrow and no one has contacted me. The phone system is completely overwhelmed and I cannot even get in the queue to wait to speak with a person. I assume what will happen is that it will appear that I just didn't turn up for my appointment, when I've actually been trying repeatedly to contact someone. They have a new online system for secure messages but when they email you they send a dodgy-looking attachment. I assumed it was a phishing email and deleted without opening but it turned out to be from Imperial. It's a clunky system - you have to log in etc. My email account is already be a secure way of communicating; please don't make me jump through more hoops just to make or change an appointment. I suspect the unwieldiness of the new system is at least partially responsible for the other modes of communication - phone and ordinary emails - becoming hopelessly overloaded.