Very often Services are staffed less than full-time and you may well receive an answering machine message. If you can, do leave a message and they will respond to you as soon as they can. Do contact London Bereavement Network if you need advice about your local service. Please also note that many services are over-stretched and may well have a waiting list. Don't give up now - you will be at the top of that list in due course.
Some services also offer support groups.