There have always been people who rang unneccesarily for an ambulance, or for that matter for a doctor.
To some extent this is unavoidable. The general public are not usuallly, doctors, nurses or para-medics, and cannot therefore be expected to assess the gravity of a situation.
Speaking as one who 50 years ago, answered the doctor's phone, I can assure you that with the best will in the world, however well trained the person answering the emergency phone is, it is not always possible to get a panic-struck relative or patient to tell you enough about what is wrong for you to be able to judge the situation.
In these cases, if there is no doctor standing twiddling his thumbs who you can send out, which there rarely is, the answer is always "send an ambulance".
It may prove unnecessary, but this is far, far better than someone dying because you did not send an ambulance.
Sending someone out to assess whether an ambulance really is necessary would only increase the risk of a patient dying unattended whilst waiting for the ambulance, so no, that would not be a viable idea.
There may indeed be an increase in calls upon the emergency services, and some of these may prove unneccessary, when someone with medical training actually sees the patient, but there is no way of preventing this, if when answering the phone, you found it impossible to gauge accurately the seriousness of the case described to you, or were unable to get a coherent account of what is wrong.
I remember my mother on one occasion asking for the address when someone screamed down the phone, send the doctor! only to discover that the caller had slammed down the phone. Recourse to the GPO, as it was then, showed the call to have been made from a public call box. My father being out on his rounds, my mother alerted the police, asking them to go to the street where the call box was, before trying to get hold of my father, by ringing the patients she knew were down for a home visit.