My cell using UK provider - EE with worldwide roaming is not allowing local Cayman calls. Is there a solution?

I’m using an iPhone X in the Cayman Islands. I’ve bought worldwide add on minutes and texts from my provider EE and can’t use for local calls but can use for calls to the U.K. Cancelled local calls say “ID4” at end of message saying “sorry the number you have dialled is unavailable”. The numbers I’m dealing are local hospital and supermarket. I’m linked to Digicel and only alternative is FLOW which has same problem.