Buffer memory, the so-called COSTI buffer, is needed in the SWU to save the call charge data for chargeable connections. The number of COSTI buffers that are set up after initial startup is dimensioned in such a way that all outgoing trunks and tie trunks can be recorded with charges.

You must expand the memory if you want incoming connections and/or internal connections to also have the charges recorded. The same applies if CDR-e is used:

COMMAND

ADD-DIMSU:TYPE=BASIC,COSTI=<number>;