Imposing your ideas on people

Sometimes, you have people come up to you and no matter what you say, they dont listen, like a sales person for example is trying to sell you something and you say.. im not interested in what your selling, get the hell away from me. But no matter what, they still keep trying to sell you their product. thats the same thing about trying to change peoples minds.. sometimes its not going to work. people have different opinions on certain things and are not going to be interested in what that person is trying to tell you... i know sometimes you only say your ideas because you care... but you cant keep grinding your thoughts into that persons head, even though you think your way is right.. sometimes they wont want to listen..