customer has two phones that have a message waiting key on them for another extension. when there is a message left there they lift the handset and press the key to log into the other mailbox. since I have upgraded them to MCD 6 this no longer works. If they press the button with the phone on hook, it works, then they can lift the handset. if they lift the handset first, then press the key, they get a busy tone and "NOT ALLOWED" is displayed. Is this something in COS? what am I missing?