You can use your iPhone to make calls, play games, and send text messages, among other things. However, you can also end up on the receiving end of text messages you'd rather not get. If this is a problem, you'll need to block the messages from that number. Unfortunately, neither Apple nor AT&T allow you to block specific people from sending texts. At time of publication, only iBlackList is able to block specific numbers on the iPhone 4. You'll need to jailbreak your iPhone before you'll be able to use the application.
Get iBlackList from iBlackList.com.br. At time of publication, the price for iBlackList is £7.80. You'll need to jailbreak your iPhone using Cydia in order to do so.
Launch iBlackList by tapping on the icon.
Tap on "Blacklists."
Tap "Add New Blacklist."
Tap the blue "+" button in the navigation bar. This leads you to a menu that will allow you to add a number to your blacklist.
Select one of the four options. "Add from Contacts" allows you to add a number from your contact list. "Add from Recent Call" and "Add from Recent Message" lets you add someone from your list of recent phone calls or received text messages. The last option, "Phone number," allows you to type in the number you want to block manually.
Select the contact you want to add from your list of contacts (or recent calls or recent messages). Or, type the number in manually if the person you want to block isn't in your contact list.
Slide the red message switch to "ON." This will block all incoming text messages from that contact.
Click the blue "Save" button to add the contact to your text messaging blacklist. After you've done this, you will no longer receive texts from that phone number.
The unregistered version of iBlackList allows you to block two numbers -- so if you only need to block one or two numbers, you don't need to pay to register.
Jailbreaking your iPhone voids the Apple warranty.