Electronic Commerce
To use on device billing, you need to become an OfficialSite. Another option is to go through a content aggregator who are official content providers on the major carriers and in turn will carry your you content for you, taking a chunk of the revenue.
Solutions
Open Source
ASP
infoDNN - Doesn't appear to have mobile support
Other
Payment Processing
Apart from using the carrier's official payment methods, there are a number of off portal payment methods, such as credit cards, bank transfer, and eMoney.