hi! Misa ,
Well you can try setting up of itemization BILL ..
incase of GSM try using the feature of ICI-1 in case of ericsson HLR .
in the MSC you will have to define a destination which will route all the CDR’s of calls having ICI-1 to that particular destination.. Take a small LINUX based PC which could poll the files from the IOG for the ICI destination say hourly bases and u can see the details as to which LAI , B-number
by this way u can see the files as soon as the calls are made ..
another way to do so it to do iofat the file incase u know which was the file in which the CDR was generated and use Ericsson Software to Decode the CDR file.