Well, if it's the same number repeatedly just block that number. By tapping the (i) logo next to the number in recent calls and selling BLOCK THIS CALLER. If it's multiple different numbers you will need to get on a DO NOT CALL LIST. Depending where you are located laws are different but also sometimes when you do business with a company that make it clear in their privacy statements that that you must agree to allow them to market other products to you. It unfortunate but true.