A method and apparatus for providing roaming and hand-off support for prepaid billing for wireless prepaid services on a data network may be provided by a first-network-access device carrying on session activity of a wireless communication session with a wireless-mobile node within a first coverage area. The first-network-access device receives blocks of credits drawn from a user account having a cache of available credits for the prepaid-services. The first-network-access device periodically measures usage of the session activity in terms of a first of a plurality of measurement-method parameters. The first-network-access device debits the usage of the session activity from the blocks of credits. After entering its coverage area, the second-network-access device establishes connectivity with the wireless-mobile node. The first-network-access device tunnels to the second-network-access device the session activity and any unused credits. The second-network-access device periodically measures usage of the tunneled session activity in terms of tunneled measurement-method parameters. The second-network-access device debits the usage of the tunneled session activity from the tunneled unused credits. The second-network-access device then establishes independent network access for the session activity. The second-network-access device receives blocks of credits. The second-network-access device periodically measures the usage of the session activity in terms of another of the plurality of measurement-method parameters. The second-network-access device debits the usage of the session activity from the blocks of credits it receives. After hand-off, the first-network-access device may receive from indications to terminate session activity, to stop debiting the usage of the session activity, and/or to return unused credits.