"Pay & Go mobile top-up
There are lots of ways to top up. Whichever you choose, you'll still get all your usual goodies, like O2 Rewards.
Here's what you need to know.
Auto top-up
We'll remember to top up your mobile automatically, so you don't have to. Step 1: Sign in to My O2.
Step 2: Choose between £10 to £30 and if you want to get topped up on a certain day/date or when your balance gets low.
Step 3: We'll then top you up automatically. You can change or cancel whenever you like.
Web top-up
Top up your mobile online. It's an easy, safe way to top up between £10 and £30. To use web top-up, you just need your mobile number and a UK credit or debit card handy.
Facebook top-up
Top up your mobile without ever having to leave Facebook. Its quick, easy and safe to top up between £10 and £30. All you'll need is your mobile number and a credit or debit card handy. Use the link or visit the official O2 Facebook Page."

а другие не про телефон

To Liquid Sun,
хамство еще никого не красило, тем более за просто так, тем более, что вы не правы - речь идет о счете для пополнения мобильного телефона, а не об аккумуляторе для его подзарядки.

To asker,
to top up or replenish

Мы из Советского Союза, прибыли по культурному обмену. Наши знают, где мы. Ищут. (с)