Phone numbers are blocked on cellular phones for a variety of reasons. There are a number of different ways to block a number, depending on the cell phone model and the carrier the cellular phone uses. For the iPhone, which is one of the more technologically advanced cell phones on the market, applications designed for a mobile device like the iBlacklist are all-in-one programs that allow users to easily block and unblock individual numbers without having to call their cellular carrier.
Turn on your iPhone. Go to the iTunes App Store and search for an iPhone application called iBlacklist. It is free to download. Press this application and install it on your phone by following the prompts that appear.
Turn on your iPhone. Select and open the iBlacklist application, or whatever call blocking application you downloaded and installed on your iPhone, to block their number.
Once it loads, go into your profile, where there will be a large number of selections to choose from. The first selection is "Blacklists" and the next selection is "Whitelists." Select "Whitelists."
In "Whitelists" go to your contacts and select the names of those you had on your Blacklist, switching them over to your Whitelist and allowing them to call you and text you. Save these changes to your profile.
Call those who you just unblocked and have them call you to test it out and make sure they will be able to contact you whenever they want.