Mixed Sino-Korean and Native Korean Numbers?

[Gudrun]

Do Koreans ever mix Sino numbers with native Korean numbers? I was taught that numbers from 100 onwards were give entirely in Sino numbers. But I read an email the other day where a Korean students says that you can mix them, that it doesn't have to be 삼백오 but could be 삼백다섯 depending on the usage. I ran this by my son's Skype conversation partner and she said that was ridiculous, that mixing the numbers wouldn't make any sense. Does anybody know of times when Sino and native numbers would/should be mixed? (I had previously thought I understood the numbering system but now I'm having my doubts.)

[julialim]

We don't mix that...

BUT! when we tell someone the numbers by telephone or something, we use better number to be sure. For example, my phone # is 321-1352.
We're supposed to say "삼 이 일 - 일 삼 오 이" .
somtimes, " 삼 둘 하나 - 하나 삼 오 둘".