Currently on holiday in Noumea. 

New Caledonia is not included in the 77 countries where VF Prepay Roaming packs work.  Extraordinary really.  Effectively the closest country in the world to NZ (Auck - Noumea less distance than Auck - Sydney).

But at least the Vodafone NZ website lists casual call and text roaming rates for New Caledonia, albeit as horrendous as they are (in Zone 3). 

But try as we may, neither I (Galaxy S8, NZ model) nor my wife (S9+ import) have been able to connect to the government monopoly mobile network (Mobilis) in New Caledonia.  Basically only have internet via WiF from our hotel.  There is a Stuff(?) article from ~2000 on the web referring to an interconnect agreement between VF NZ and Mobilis.  And according to https://www.frequencycheck.com/ my phone at least, is 100% compatible with Mobilis frequencies (did not check wife's S9+ but likely same applies?).   

Our hotel phoned the Post Office here in Noumea and they confirmed that they have an agreement with VF NZ.  They suggested that perhaps it was because I had data roaming turned off !!?  Yes, indeed (well on National roaming only.  Not paying $10,000 per GB for data).  Not certain why that would be relevant to connecting to the mobile network.  But just to check, in the safety of our hotel room (Wifi on!) I switched data roaming back on and of course it made no difference.  

Attempting to manually force a connection to NCL MOBILIS gives the following response: "Your SIM card does not allow a connection to this network".  Speaking with a local phone shop, they said 'no, NZ phones will not work here".

The night after we arrived (~4 days ago) I spent an hour or so chatting with two VF Ninja's.  The second of these 'raised a ticket' and said they would let me know via txt (!) what the issue was. Had to point out that I had no network connection so cannot receive any txts (the whole purpose of my contacting them - 'oh, yes').  So he took down my email address and said they would contact me by email.  I have heard nothing since so that seems a dead end (assuming some bright spark there has not sent advice via txt anyway).

Of course we could get a (not cheap) local SIM to provide data but it would not be particularly helpful.  We can survive sans data away from our hotel & restaurants etc.  Basically here to relax and not going far beyond Noumea.  My main concern relates to the likes of dual factor ID etc (as well as unexpected business & personal calls) where I need my NZ mobile number to be active.  Especially for banking.  Also being hounded by MS wanting me to verify my activity as they have detected unusual activity ....!  But I cannot because, to verify they send a txt to my NZ phone number ...  Etc (Why oh why, happens every time I travel overseas.  After 20 or so times you would think they would catch on that sometimes I do travel overseas).

Has anyone been to New Caledonia and either had a similar experience, or actually managed to connect to the Mobilis network?

Anyone from Vodafone or otherwise know what I need to do to connect?

Is it possible. Is there something I am missing / need to do?

If not possible, why list casual roaming rates for prepay.