According to Verizon (my carrier) you can only block a few numbers, I think they said 5. You have to log in to your account online, then go to your settings, and you will find a place to fill in phone numbers. Last I checked, I think they actually allowed up to 10 or 15 numbers. The problem is that you have to do this every month or so. It is a big pain. I use my cell for business so I get a lot of spam/sales calls. It seems an inefficient way to serve their customers. Also, another thing you can do is list your number with the national do not call list. You can google it and do it online. Sadly, I have done this, and it hasn't really helped that much.