Different services vary in what they offer, but in general you can ring up and speak anonymously to a counsellor about any sort of problem in a no-pressure context that's less threatening than a face-to-face session.
Talking the situation over with a caring, independent person can be of great assistance whether you're in a crisis yourself, or worried about someone else who is, and they usually have connections with local services to refer you to if further help is required.
You don't have to wait until the deepest point of crisis or until you have a life-threatening problem before you seek help.
Demand for telephone services vary, so the most important thing to remember is that if you can't get through on one, keep trying several until you do. You should usually get through straight away, but don't give up or pin your life on it.
Many people that feel suicidal don't realize that help can be so close, or don't think to call at the time because their distress is so overwhelming.