To block calls on your Curve:

1) In the phone, press the Menu key
2) Click Options
3) Click Call Barring
4) Highlight the call blocking option you want
5) Press the Menu key
6) Click Enable
7) Type your call blocking password.

To stop blocking calls, highlight a call blocking option, click the Menu key and select Disable.

Please note that call blocking is not associated with your device, but instead with your carrier and your SIM. You will need to contact your service provider to purchase/enable call blocking – they will provide you with a password for the set-up listed above (which, by the way, I lifted directly from my Curve – must give credit where it is due!).