[scanapa]

Hi, I understand that to block a number from incoming, I need a SIM & the carrier to set the phone up. Which carriers can do this? AT&T told me that cannot. This is for a 9900. thanks!

[SmellWhole]

Well, if you like, use, and trust apps on your device (I don't), there are call blocker apps in BlackBerry AppWorld that can do this. If I don't want to be bothered by someone's call, I just set up a contact for the caller and make his ringtone silent.

[jegs2]

I purchased iBlocker Pro from App World, and it works like a champ.

[xanadome]

I have been using "Call Filter Pro" over a year and it's flawless.
It blocks unknown, private, 800 calls, and whatever other number you enter.
If you set it "pickup & hangup, unwanted caller cannot even leave a message.
Rogers provide an ability to block unknown, private and 10 or 15 numbers of your pick. It of course blocks those calls at the carrier level (before even reaching your phone) but it gives callers a pre-recorded message, which says something to the effect that "a person you called is not presently available".
After I started using the call blocker, those spam calls almost stopped. They seem to give up calling me at their first attempt. I get those "free cruise" calls etc once every 3 months or so (phone shows callers' numbers and I simply punch it in Google, and I know who the scammers are that way). Blocking 800 numbers works really well, as it blocks Rogers' promotional 800 calls, LOL.
There is also a free web based voicemail program (YouMail) that also avoid unwanted calls.