Hi Alan, do you have already check these commands:
aaa accounting connection h323
To define the accounting method list H.323 with RADIUS as a method with either stop-only or start-stop accounting options, use the aaa accounting connection h323 command in global configuration mode. To disable the use of this accounting method list, use the no form of this command.
aaa accounting connection h323 {stop-only | start-stop | none} [broadcast] group groupname
no aaa accounting connection h323 {stop-only | start-stop | none} [broadcast] group groupname
Regards.