Carrier billing is coming to more than one telco in Malaysia. Digi may have announced that it now supports the payment option, but Celcom and U Mobile have also been spotted as options in the iOS settings.
What this means is that customers from one of the three telcos can now charge App Store purchases to their carriers instead of a credit card. Something especially useful for those who would rather not use cards. Carrier billing works on both prepaid and postpaid plans for all three telcos.
This leaves Maxis out as the only large Malaysian telco to not support carrier billing on the App Store. That said, it should only be a matter of time before the announcement is made.