There are some programs (my cable company has one) that will "vanish" Robo calls. The phone will ring once and that is it. You might want to let ALL calls go to voice mail set the pick up at 1 ring. That way he does not get a chance to answer the phone. If it is an important call you can call right back if you are home at the time. If this is a cell phone if you can block all calls that do not come from a "contact" that might solve the problem.
Problem with no land line is there are some 911 centers that can not pin point a cell phone call so in an emergency the dispatch time might be greater is they have to go through a series of questions. And if your phone is not from the same area code it may get sent to a much more distant dispatch center.
You might want to let ALL calls go to voice mail set the pick up at 1 ring. That way he does not get a chance to answer the phone. If it is an important call you can call right back if you are home at the time.
If this is a cell phone if you can block all calls that do not come from a "contact" that might solve the problem.