If anyone has a O2 contract, you can cancel now penalty free. This is what you must do:
Write a simple letter to their disconnections department (USE ROYAL MAIL RECORDED DELIVERY)
Write in your letter that because O2 has changed your terms and conditions using charging for ringing 07744 & 07755 numbers that this put`s you at a disadvantage under clause 8.4 c of your terms.
At the moment O2 let you ring 07744 & 07755 numbers out of your free x minutes, but from the 1st July they will charge you 25p a minute.
This is your get out of contract free.
Hurry and get the letter in the post.