SL1100 system with Normal POTS lines, except for one DIL line that rings extension 1103. Callers leave messages in 1103's mailbox.

The customer has trouble getting to his mailbox from home. I should be able to press # # and the extension number to login, but instead it sends me to the other line's DAT as if I pressed 1.

If I wait a couple seconds between key pressed, I eventually hear the canned voice say "enter a mailbox number". Then we're ok.

Thanks for any help.
Jim