Apple has slowly been expanding mobile phone billing (or carrier billing) to additional countries, and three more have been added to the short list of supported countries this week. Customers in Austria, Italy, and Singapore can now use mobile phone billing with select carriers where available.
Mobile phone billing lets customers roll charges for the iTunes Store, App Store, iBooks Store, and Apple Music memberships into monthly phone bills from the carrier as an alternative to storing debit or credit cards with Apple.
These carriers work with mobile phone billing in each new country:
Drei in Austria
3 in Italy
M1 Limited in Singapore
You can find the full list of supported carriers in previously supported countries including Belgium, Germany, Japan, Norway, Russia, Saudi Arabia, Switzerland, Taiwan, and UAE on Apple's support site.
While the concept has been available from other companies with various carriers in the United States, Apple does not support mobile phone billing for the App Store and other services in the US.
Source: 9to5mac