Anonymous Call Rejection needed for the iPhone

Someone keeps calling my mobile phone number. Their phone number is blocked from showing up on Caller ID. They hang up if I answer, and don’t leave a message if I don’t answer. It’s happened six times so far today.

Amazingly, neither the mobile device (an iPhone 3GS) nor the carrier (AT&T Wireless) will let me filter out such anonymous calls.

Anonymous Call Rejection is a feature available on most landlines and VoIP systems. If you call my landline office number, and your phone has Caller ID blocking, you’ll hear a message from AT&T telling you that my phone won’t accept your call.

However, at least in the U.S., no wireless service offers ACR at the carrier level. I don’t know of any mobile phones that implement it at the device level.

This is a software limitation, not a telephony problem, since the iPhone displays “unknown” when someone without Caller ID phones me. Thus:

• AT&T Wireless knows there is no Caller ID — so why can’t it filter the call at the carrier level?

• The iPhone 3GS knows that there is no Caller ID — so why can’t it block the call at the device level?

There are plenty of settings on the iPhone that affect the AT&T Wireless service. For example, I have a setting, right there on the iPhone’s control panel, to choose to block or transmit my own Caller ID information when placing a call.

But ACR? No. Sorry, said the representative at AT&T Wireless, we don’t offer that.

(There are hacks that enable Anonymous Call Rejection on an iPhone that has been jailbroken, but that’s not something that I wish to do. I don’t want to hack my phone. I want a fully supported ACR feature offered by the carrier or by the device itself.)