To hear a phone or the door bell ringing in your dream generally represents a good omen related to good news about the increase of your gains or from people you love. If you manage to answer the phone or the door and the person you hear/ see is someone you know and care for, this foretells prosperity, success and happy events to follow into your waking life. If the person you hear/ see is a stranger, this may stand for changes for the better or worse to take place in your life soon. On the other hand, to hear/ see someone you do not like, an enemy or competitor, this may be interpreted as a bad dream omen forewarning of false and untrustworthy friends who attempt to feed off you.
To hear something loudly ringing in your dream, frightening you, may also stand as a warning signal which tries to make you become more self-aware (gain more self-confidence) or grow more aware of certain situations/events in your waking life. Try to read between the lines and find answers where you never thought you will find them - the loud sound tries to 'awaken' you.
If you are the one desperately pressing the door bell or calling someone, this stands for your need to express yourself and communicate with the others. Such dream images are very frequent among introvert people who find it difficult to speak their mind and be open with those around them.