If you block your number they have no idea what number to remove from the list..So legally thecompany can call you back until you specify which number to remove. If its a legit company the generally comply with DNC requests. If you are dealing with scams which sometimes can be ran from overseas just be nice. If you get rude they will not stop calling and will pass along your info to other organizations. Even requesting nicely doesnt always work. But, you catch more flies with honey than vinegar.