You actually have 4 options, 1) Pay AT&T (and soon Verizon) for a service that blocks numbers 2) Use the silent ringtone method (that what this article is all about!!) 3) Port your number over to Google Voice (GV) and block the call on the Google Voice side 4) Unlock your phone and use iBlacklist this is a true call blocker and costs $12.
The bad news is that there is currently no FREE way to block a particular phone number from calling your iPhone. AT&T appears to offer a paid service called "Smart Limits" that allows a user to block numbers but it's $5 per month / line and why should we have to pay for this!
The method I'm going to describe here is called the silent ringtone trick and no, I did not come up with the idea even though almost half a million people have read this article! Dead simple idea really, grab a new ringtone off my site called Silent Ringtone then assign it to the bugger err number you want blocked. The silent ringtone is actually a real 30 second ringtone that consists of 30 seconds of sweet Fanny Adams i.e. pure silence. Your phone will ring for all other calls, except the ones assigned to this silent ringtone! (See gotchas at the end of this article)
Here it is in three easy steps:
1. First download file by right clicking (or command clicking apple users on this special secret SILENT Ringtone download link IMPORTANT --- Missed list. If you phone is on vibrate, it will vibrate when the baddies call but not ring; this may be annoying.
They will still be able to leave you a message (most telemarketer won't) BUT the phone will never again ring when they try to call and harass you, out of sound out of sight perhaps??!