Crosstalk vs interference
Crosstalk is a type of interference.  Interference can come from just about anywhere - e.g. RF interference from all sorts of things emitting radio waves (including, but not limited to, radio transmitters).  Interference can also come from coupling from other devices.  In the case of a phone system, this could be hearing humming from a power line or music from the local AM radio station on the phone line.  Generally crosstalk refers to interference from an 'adjacent' signal - be it in a wire, radio channel, etc - leaking into the 'victim' signal.  In the case of a phone system, this could be in the form of being able to hear your neighbor's phone calls on your line because the two lines are routed next to each other on the telephone pole.