Ask your phone company how to list your number so you cannot be identified. If you can't afford an unlisted number, ask the phone company if you can be listed under a different name with no address.
Find out how to get a "private number", i.e., to block your phone number from appearing on the caller identification box of the person you're calling. Check periodically to make sure it continues to be blocked. Be sure your fax machine number is blocked too. Test whether your "private number" can be reached if someone dials automatic call back. Check internet databases for information about yourself and inquire about ways to keep information out of public databases.
If your abuser continually calls you:
Regular and cell phone records can be used as evidence of harassment.