How to block someone's mobile number?

Basically I just want to block someone's mobile number because they keep calling and texting me and some of it is quite abusive and I just can't deal with the hassle. I'm on O2 UK but I don't think they can block somebody's number without having to change your sim or your own number. Now I believe the new iOS 7 update allows people to block numbers from calling and texting you, however I haven't done the update on my iPhone but I have done it on my iPad so is there any way to block it on my iPad and link it with my phone or is that just wishful thinking? Any help would be much appreciated, thank you:-)

Do you have verizon? I know how to block it with verizon

Download an app true caller. It provides the option of blocking the numbers.

You can't link the blocking across those devices since the iPad lacks this feature for some reason.

Even if it did support blocking, it is unlikely that it would work without upgrading your phone to iOS 7 as well.

Sorry but no blocking from ipad, if you do update your phone tap 'phone' then 'recents' at bottom, all you recent calls will show up with a letter i in a circle on the right, tap the i symbol and scroll down to the bottom of that menu and you will see the option to "block this caller" tap that and job is done.