Rob Griffiths, during a chat the other day, found that if you press and hold the 0 button on the number pad, it types a + character. So to make an international call, all I need to do is press that button, then enter the country code and the number. This will make my international calls a bit easier, at least for people who are not contacts, and who I don't want to make contact cards for.
It's worth noting that pressing any of the other keys, the ones that show letters, such as ABC, only types the number. I guess the fact that the + is on the 0 button makes one think there's a way to get it to display; I had tried in the past, but didn't hold it long enough.

