While you wait for answers, we may have found some information which could help you.
Click here for Bt Studio 1100 PhoneHow can i show calls made to my phone?
BT Studio 3500 base problem?
Bt 3500 cordless tel/answerphone?
How do I connect my own answering machine?
how can i fix a bt graphite 1100phone?
Permanent engaged tone on BT Studio 1100 handset?