SMARTPHONE USERS: This should manage hundreds of PHONE/SMS text message bad people for free.
Step 1: Create a contact A_SPAMMER (or more humorously, AN_IDIOT). Set its ring tone to NONE or SILENT.
Step 2: Add every phone number (or text message ID) you wish to 'block' to the A_SPAMMER contact.
Step 3: Manage incoming calls by setting your DO NOT DISTURB features to only allow calls/text messages those in your contact list. This will prevent ANY call from disturbing you, including those who hide their phone number or text message ID. If it is important, they will leave a message with their contact information. Make sure your outgoing voicemail greeting demands a callback number to assure good callers will give you their number.