On a land line, contact the phone company and add Call Blocking to your phone, then program his number in to it. On most cell phones, you can do this from your address book, select his number and add block to it.
There's two means of technically blocking incoming calls assuming the caller does not suppress his calling ID: Either by having the telecommunication provider block that number or by blacklisting the caller ID within the software setting scope of the telephony device in use.
start with the phone you own. moost newer phones come with an option to block a numbers as do cell phones. some prompts will be to ignore some will list it as block. if all else fails call your phone company and have a permeant block put on your phone,