Is the system set for forced accounbt codes or is Telco?

Also, how is the call transfered offsite, from voicemail or a PhDN that is Call forwarded offsite.

If the CIX100 is using forced account codes, I would setup a new COS that does not have forced account codes, make sure voicemail ports are using this COS (If the VM is transfering).

Also using system speed dials may be the best bet to eliminate account codes. I have not tried it, but you can try enabling Speed dial overrides DR in program 105, and setup speeddial to use the COS without forced account codes in program 509.