Re: Iphone 4
Your carrier may allow a certain number of blocks. Verizon allows 5 number blocks for free. If you have iOS 7, you can block numbers that come in as a call or text. Calls: go to recent calls and tap the circled "I". Scroll down to Block. With text you tap Contact in upper right, then tap the circled "I". Then scroll down to Block.
Sent from my ancient but trustworthy iPhone 5