Mr. Number is a free app you can download on your smartphone to block unwanted calls and text messages. You don't need to pay AT&T or any carrier anything to block unwanted calls.
Also, if you have home phone service through your cable company, you can block calls from the web for free.
Actually with android phones you can block without adding anything. Bring up the number you wish to block, instead of clicking add to contacts just hit your menu button at the bottom and it will open the menu with an option to block the number. Your phone will not ring when the number calls, it will show that they called in your call logs but it will not ring and it will tell you that the number was blocked..
You can also get a call blocker called Digitone. I bought one about a year ago on the net for about $100. It stores up to 80 numbers (and entire area codes, if you wish). When you get a call from a number you wish to block, you just push the block key twice to record. You can also program them individually. Any fake numbers (000-000-0000 for example) are automatically blocked.
You can set up VIP numbers for numbers you want in. You can set up times to not allow any calls at all, except for VIP numbers. If the phone spam gets any worse, I'm thinking about changing my after hours setting from 9PM-6AM to 3:00PM-2:59PM and just block ALL calls, except my VIP list. The VIP list is limited to 30 numbers.
When a blocked call comes in, the Digitone answers the call before it rings the handset, gives them 8 seconds of silence, and then hangs up. Highly recommend.
Hey, try going to your service provider's website. I use sprint for my iphone and I can block up to 20 numbers. I'm not sure about AT&T but you can call them. Good luck.