Verizon has on the site how you can block a number but it is only for 30 days.
I don't know if Sprint offers this. I recommend you change your phone number. I know this can be a drag,but you can text everyone or email them with your new number. I think this will be your best bet.
I am sorry Sprint is not being more helpful to you.
If they say you have to pay a fee to change your number, ask to speak to a supervisor and request no fee and explain why. Verizon doesn't give problems to changing a phone number.
Maybe you need to switch carriers. I sold Sprint and Verizon and Sprint really needs to come to bat for their customers more.
somebody is constantly stalking and calling me sprint wont help can i block the # using any features on my blackberry