Some companies who order transcription services want the en dash while others want the double dash. The easy way to take care of that is this in Microsoft Word: Format, AutoFormat, Options and then on the AutoFormat tab you tic the box "Hyphens (--) with (–)"

Now for it to work as you type, you also need to go to the AutoFormat As You Type tab also and tic the same box.

Boxes tic'd means en dash (–), boxes not tic'd means double dash (--). Also when you do en dashes this way, they don't change, as you're typing, from double dash to en dash until after you type the next word and then hit the space bar, then it changes.