Constant harrassment for a new contract

I have an average of 20 phone calls from elite mobile on this particular number "+***" per day ... Up until last week I would take the call and ask them to stop calling as I do not want another contract or to change my service provider ... Since Wednesday last week the caller has been becoming more rude and it has come to the point that I have to block this number as I do not have time to tell elite mobile EVERY TIME that I am not interested in any promotions , contracts , change overs etc ... I do not know where they got my number from but it has put such a sour taste in my mouth about them that I do not even want to consider using them in the future as NO MEANS NO! But to them it means let's see how many more times we can call this potential customer. Very sad that they have gone to these resorts to try get a customer even after numerous times one has said no to there services