I am sorry to say. But it is not possible to block a phone number as it is to block an email address and if so it was possible do you think that person will hide their number and call you. I suggest speak to the person tell them to stop calling you. Or get a new number if the person somehow gets you number you have to take it a level higher. Contact the authorities in someone countries there are serious laws against what the person is doing. It is like an early form of stalking. Hope I am not alarming you.