Help with BT Phone?

BT Studio 1500 with answer phone

I wonder if you can give me a bit of advice. I bought the above phone from e bay. When I received it I charged it for a day and when I turned it on and plugged the line in there was no dial tone. The answer machine works and so does the phone if somebody is ringing in from outside the house. But although I can hear the phone ringing, I can't answer it or use it to make a call.

Can you please tell me what could be the problem. I have downloaded the user guide from BT web site but nothing seems to make a difference. Now the man I bought it off won't answer me. Please help.