There is a way to block certain numbers from sending SMS messages, but I don't believe Sprint can block individual numbers from calling you. One thing you can do is add the undesired number to your address book and set the ringer to silent. Hope this helps! Here are the directions for blocking a number from sending you text messages:

To block messages, specific phone numbers, email addresses or email domains, sign on to My PCS. Select My Online Tools > Text Messaging > Settings and Preferences. You will find the option to block messages in the section entitled "For SMS Text Messaging Only". (from sprint.com)

hi - can anyone tell me if there is a way to block a certain phone # on the Samsung Blade through Sprint?