Around one-and-a-half million customers on O2's O2 Refresh tariff will have their bills drop by an average of £18 a month each as the network celebrates its second anniversary of the price plan by slashing fees.

The customers who will be affected are those currently on an O2 Refresh tariff, which allows them to pay for their phone and mobile plan separately. It usually allows for customers to upgrade their handset by just paying back what they owe for the device itself, rather than the total contract, but it has been revealed that many customers on the tariff are keeping their devices even after they have paid for it in full.

Around 1.5 million customers, in fact.

O2 is therefore ensuring that customers do not have to pay for their handset as part of their monthly bills if they have already paid for it in full and don't want to upgrade. They will only have to pay for the talktime, texts and data plan they signed up for.

As the O2 Refresh tariff has been around for two years, and contracts were 24 months long, that means all of the customers who signed up at the beginning will see large savings. Unless they want to subsequently get another phone, of course.

The same will be true for newer customers on the O2 Refresh tariff when their initial contract expires. Although that's subject to any plans Three's owner Hutchison Whampoa might have for O2 if its proposed buy out finalises.