Pretty frustrated with O2 just now. I ordered a new PAYG handset on the 23/11. It arrived on 28/11, and after a couple of days playing around with it, I decided that I don't like the phone. I called Customer Service this afternoon to enquire about returning it, and was told that wouldn't be a problem, and that a returns form would be emailed to me right away. After a couple hours the email still hadn't arrived, so I used the 'Live Chat' option to further my enquiry.
After I was given the direct link to the returns label, I asked if he could confirm that a Return Request had been logged on my account, as I just had a feeling that the agent I spoke to over the phone about returning the handset, hadn't logged the request on the system, and had not bothered to email the returns label link. After giving the 'Live Chat' agent the order number, and answering a security question, he still wouldn't confirm if the returns request had been logged and authorised, and then started to tell me that I wouldn't be able to return the handset, as it has been more than 7 days since I placed the order. I pointed out to him, that the O2 website says.
"If the product you've bought from us isn't quite what you wanted, you've got 7 working days to return it back to us."
It has not been 7 working days since I placed the order, it's been 5. Also, it doesn't say that it's 7 working days from the order being placed. I would assume that it's 7 working days from delivery, as sometimes things take longer than 7 days to arrive; especially to rural areas. The delivery is digitally signed for, so O2 know exactly when it was delivered.
I've been a loyal PAYG O2 customer for over 10 years, but that obviously doesn't matter to O2. If that's the way O2 want to be, then I'll just have to take my business to another supplier. 
Update: Just spoke to Joanne and Eddie at customer service, and all issues have now been resolved. They were both extremely helpful. Whoever I spoke to yesterday did nothing about my returns request, and I really wish I had taken their name now, as they didn't log the request on their system. A note has now been added to my account, saying that I have called within the 7 working days period, so there shouldn't be any issue. I will post an update if it all goes wrong.
Again, thanks for all the advice, it's very much appreciated 
