Q: how to block a number on iphone 4

http://support.apple.com/kb/HT5845

This URL is for IOS7 only!!

Call and message blocking is a feature of iOS 7 - if you are unwilling to upgrade your iOS, then you cannot block anything on your iPhone.

reefer01 wrote:

 

This URL if for IOS7 only!!

The OP has stated in the additional info line of iOS 7 usage, so the reply applies to this case 100%. Threadjacking without even providing adequate info won't get you very far.

Well...thank you very much Michael Black! You have not only confirmed my message, but have totally confused me by your succeeding comment!!??!!?!

Sorry, what is confusing?  Call and message blocking are features introduced with iOS 7.  No previous version of iOS has that feature.  So of course the URL links to a description of call blocking in iOS 7 only, as only iOS 7 has that feature.

If you are running any  version of iOS prior to iOS 7, then your only option for call blocking is to contact your carrier and ask them if they offer blocking services as you cannot block anything on the device itself.

It is not possible to block contacts in iOS 6.