Cancelled account within cooling off period but still being charged

[Cannon]

After several hours on the phone a few weeks back I managed (so I thought) to cancel my o2 account. However, I’ve still been charged. Any idea how I can deal with getting a refund that avoids 3hrs on the phone to a customer service agent that’s less than helpful please? Thanks in Advance 

[MI5 · Accepted solution]

@Cannon 

You need to contact payment management.
Details here Guide: Coronavirus Community Help and Support 
To pay bills, ask for payment extensions etc, you need to contact the Payment Management Team.
You can reach the Payment Management team on 0800 902 0217.
The opening times are:
Monday to Friday – 8am to 8pm
Saturday – 8am to 6pm
Sunday – 9am to 6pm
https://www.o2.co.uk/help/account-and-billing/payment-support
Best time to call is around 8.00am