Wow, is that 4-5% of ALL ambulance use across the whole of Wales? Divided by 10, that's very nearly one call every day of the year - so the person at number 1 in the list almost certainly calls multiple times, every single day.
Considering that ambulances are intended for emergency cases - a high proportion of which will mean, sadly, that the patient will already be too ill to survive, in spite of the very best efforts of the paramedics and the hospital.... it does rather statistically suggest that they weren't genuine calls: I highly, highly doubt that, across the ambulance service as a whole, out of any random 365 admissions to hospital following an ambulance call-outs, every patient would survive.
It sounds like each trust needs a dedicated section to deal with these people and give them the help (or prosecute them if merited) that they need. When I worked in accounts, we had a general helpline number for about 99% of clients, but a separate team who looked after the rest - only 1% of the clients, but representing maybe 40% of all the business turnover.
If very frequent clients of Social Services have their own named case lead/contact to deal with their ongoing situation in an appropriate way, why shouldn't it be the same with constant ambulance-requesters?
The whole idea of 999 is that any one person will call them out very infrequently (if ever at all) - maybe moderately, depending on their personal circumstances; but the nature of a proper emergency is that they should be rare in any one person's life. Nobody has multiple genuine emergencies every single day of their life - if they believe that they do, they really need a dedicated case worker, who can refer them to the NHS help that they likely do need or, of course, send an ambulance if it is actually needed. It must be far cheaper and more helpful in the long run.
It's got to be a massive red flag that something isn't working properly when the most frequently-called number on a person's 'friends and family' list turns out to be the emergency services.