In Reply to: Yes posted by GaryD on Friday, 8. May 2009 at 18:40 Bali Time:
I once had to try and do it myself, and it was really complicated! In the end it turned out that the sim had expired which is why it wasn't working.
Make sure they do it for you and test your phone is working by calling them before you leave.
The stall Gary mentioned are helpful - but no need to make a special trip if you are not near Matahari. There are lots of places advertising credit for mobile phones. Almost every hotel will have one or two within close range.