NO FOR AN ANSWER

Why is it that some people just cant take no for an answer? Recently met a couple from RHP dont get me wrong nice people. However when told not going any further, texts continue and phonecalls continue to the point of ridiculous. now causing problems with relationship as a result of not being able to accept no for an answer. HAVE SOME CONSIDERATION why do people do that? If they had said no would they be happy with our doing this to them? i think not No is No