the number system changes to one you don't recognise

Man, that one's aggravating. I didn't even think it would be considered weird to want my phone's UI to be in my own language, but for phone numbers to appear with formatting appropriate to the country they're for. Shoehorning every number in "contacts" into US-style 1-XXX-XXX-XXXX just because I report that I speak US english is a usability disaster.