Anyone that is currently on the O2 Pay as you go service can claim their O2 Reward as of July 4th (Today).
As long as you are registered to O2 Rewards you will be rewarded with 10% back of all your top ups over the last three months. I for instance just claimed £7.00.
To claim your Reward simply call 313 free and press 1. Your calltime reward should be applied to your balance within 24 hours.