What is one word to describe the person being called via phone?
callee (if you want to go with a single word)
one who receives a telephone call
Though this term is usually used in computing.
There is also called party which is more related to your context.
The called party (in some contexts called the "B-Number") is a person who (or device that) answers a telephone call. The person who (or device that) initiates a telephone call is the calling party.
Receiver can be used but sounds odd. I prefer recipient.
Consider:
The number's new user has requested to be removed from our calling list.