0371 numbers are not free to call for O2 users or customers on any other mobile network. However you can use free minutes from your monthly allocation as calls to 0371 numbers are charged at the same rate as calls to local numbers.
Who uses 0371 numbers?
0371 numbers are used as national customer service helplines throughout the UK and became far more popular since Ofcom legislation was altered in July 2015. This change in the law made it illegal for companies to use the more expensive service numbers such as 0845 and 0870 as post-sales helplines.
O2 call costs – 0371 numbers
Inclusive minutes provided by O2 can be used to call all 0371 numbers for no additional charge, making them essentially free. However if you do not have these minutes on your O2 tariff you will have to pay an access charge of between 30-35p as well as a similar per-minute fee.