Ahead of its 5G rollout O2 has followed rivals in offering unlimited data plans. They're available on both its Custom Plans and SIM-only deals. Starting at £33 a month, they aren't as low-priced as many other competing tariffs, however, and are restricted to certain handsets. 

The offering is for 4G tariffs at present, but there will be an "unlimited handset tariff option" when the company starts to roll out 5G next month. The new tariffs are available on O2's 5G-ready phones, the Xiaomi Mi Mix 3 5G, Samsung Galaxy Note 10+ 5G and Samsung Galaxy S10 5G

Unlimited data is also available as part of the Family Plan, including the O2 Family discount as well as O2 Open and O2 Students plans.

Three has been beating the unlimited data drum for some time, notably with it's mid-decade One Plan offering which it had to kill after a few users abused the service. The network now once again offers tariffs with a 1,000GB a month fair use policy and is set to extend this to 5G at no extra cost. 

When Vodafone launched 5G in July it too came out with unlimited 4G/5G tariffs with the intention of besting key rival EE. However, EE then retaliated with unlimited 4G/5G data tariffs, too, meaning that O2 is the last of the big players to go unlimited in some way. 

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