Local contacts show as foreign phone numbers with an eSim

I recently updated to an esim in order to buy local sim cards for data when travelling. My phone is Slovenian and I recently travelled to Brazil, Argentina (1st trip), Singapore and Australia (2nd trip) where I managed to use local sim cards with mixed results. After returning home from the first trip I noticed that local Slovenian contacts (all entered with +386) started to show as a number only from Brazil.

Things gort stranger after the second trip, as the phone took a while to realise that I was back in Slovenia. it eventually did revert to Slovenia, however on a trip to Hungary then switched back to Singapore Changi Airport. That issue has resolved itself, however local contacts are now showing only as numbers from Singapore, which is really frustrating as I have no idea who is calling.

I did a lot of research on the internet to no avail and have turned icloud on and off, and even restored the phone to factory settings and then a backup.

I can't help thinking that this is something to do with the esim as I've travelled extensively with all iPhone models and even this one before I changed to esim and never seen this before.

Any help would be really appreciated!