A phone ringing can represent: a real, imagined, desired, or feared communication (or other contact) with another person; a request for your time or attention.
A bell ringing can represent: a message being delivered (such as a school bell announcing the end of a class period or church bells signaling a special event); a message to pay attention to in the dream or in real life.
See also: Communication; Phone; Chimes; Loud; Noise; Warning