Technically 0333 numbers are not free to call on O2 as they are charged at UK standard rates, however this means you can use any inclusive minutes on your O2 bundle or rewards package to call them for no additional charge.
Who uses 0333 numbers?
0333 numbers are national non-geographic helplines which are used by organisations throughout the UK as post-sales helplines, which you can use for any manner of customer service enquiry. These numbers are highly popular in the industry as they are easy to memorise for their customers, plus legislation passed by Ofcom in July 2015 made it illegal for companies to use numbers beginning with 0844, 0845 and 0870 for after-sales support due to their higher costs.
Cost of calling 0333 numbers from an O2 mobile
Calling an 033 number from an O2 handset will cost you 30p per call no matter which tariff you are on as well as a per minute fee which currently stands at 35p per minute for pay monthly customers and 30p per minute for customers with O2 Pay & Go. However as stated if you have free inclusive minutes on your O2 bundle or rewards package you can call 0333 numbers for no additional charge (other than the minutes you use up in the call) as these numbers are covered in your terms and conditions, which saves you a considerable amount of money.