iPhone phone spam blocker

The iPhone doesn't have the "block calls from this number" that Android and other smart phones have. If you want to block a number, you have to buy a $5/mo (or more) service from AT&T.  There are apps which can block calls, like iBlacklist, but they're expensive-ish, (for apps) being $12 or more.

What you can do on your own is this:

1. Download a "silent" ringtone.  Here's one.  Save it in iTunes (Firefox, choose to Open it in iTunes). 
2. Sync your phone. If this is the first ringtone in your iTunes, you'll see a new tab called "Tones" in your iPhone panels where you choose what to sync. Sync over the new silent tone. It's called "Silent Ringtone".
3. From your incoming calls, find a spam phone number (or enter it as a new contact if you know the number)
4. Set the First Name to "9-[Spam Numbers]".  You put the "9" on the front so it sorts down to the bottom when you're browsing contacts. Make it a pirate-eye-patch frowny if you want. 9^{  
5. Choose for rington your new "Silent" tone.  Your custom tones sort to the top of the list, so it should be above "Marimba" (Apple's default) at the top of the list. 
6. Set the Vibration to be none. The "None" vibration is at the bottom of the Vibrations list. Do the same for Text tone and vibration, in case the spammer tries to send an SMS. 
7. You can even assign a spammy picture for it, in case you're looking at your phone when the silent call comes in (or you happen to be on another call and pull it away from your face to check when you get that momentary interrupt for a new call).
8. You can't do it when you're setting up the initial number, but if a new spam call comes in, add it to Existing contact and keep adding numbers to your "9-[Spam Numbers]" contact.