Dial assist is enabled, but I think that is required. I travel for work and call people in other countries, including when roaming.
Everything has been fine since I joined about a month ago, but just this morning I got an iMessage from a friend and the alert on the phone gave his name as 'Maybe: contact name' instead of just the usual name. I tried to reply and that didn't want to know either. Then I looked into it and noticed the formatting of the numbers in the contact (including others, not just his) was all messed up, looked on here and there are some messages with similar-ish issues.
I restarted the phone and the issue has gone away (contacts have re-formatted to UK again), but it does indicate that something may have changed very recently, probably overnight last night. I don't see SIM Applications any more, for one thing.