Top up by phone:

Dial 150 from your EE mobile. Follow the voice instructions.
You’ll receive a text as soon as your call credit has been topped up.
Top up by text:

Send a text to 150, containing the following: VO[space][the 16-digit voucher code we sent you]. For example: VO 1234567891234567 (without gaps in the voucher code).
Top up from abroad:

You can call 360 from your EE phone or +44 7953 966 250 from any other phone.

For the full legal terms, including the 180-day activity requirement (to prevent SIM deactivation) and the 6-month validity period of E-Vouchers, please visit:https://ee.co.uk/help/terms-and-conditions/mobile/pay-as-you-go