My 2 year old Samsung has decided today not to charge. It would only recognise 1 charger when at 15% but would only stay on charge for about a minute. I have tried it in different sockets and also the same charger in different devices. My phone is now completely dead and will not charge. I would be very grateful for any help.
You could try carefully cleaning the charge port with a cotton bud or cocktail stick to see if there is any fluff in there. Some switch cleaner may also help if you have it.
Otherwise, I would seek help from Samsung.
Try a different charger and a different cable to start with, as this will rule out the charger and cable
If still no joy then contact Samsung Support direct they will be able to support better, than o2.. although I will warn you if the phone is out of warranty then it may be chargable