Answering machine doesn't work.

Our home phone (A GE 27851FE1-B) seems to be running into problems lately. First off, the answering machine does not work. We lost the manual, and forgot how to set a voice announcment, but it should have a default automatic answering machine, but it doesn't work. When someone calls our phone, they still get an answering machine, but we don't know what machine that's going to, and we certainly cannot hear it. Yes, the answering machine is on.