I have a Call pilot 100 with 10 Mailboxes on a cics

I created 4 Subsciber Guest(no phone) Mailboxes and Two of them work fine,but the other Two I can not leave a Msg when I call in on a Back door line which gets answered by the main company greeting and dialing the mailbox # 253 or 254
its says "The person you are trying to call is not avaiable " then I get return to main greeting
I am able to log on to the mailboxes and check for msgs
any ideas
Thanks
djohndi