How do I buy add one when I am on contract

[Maxi74]

Hi guys how do I pay for add ons for calls to the U.K I’m in Thailand  but want pay upfront x

[Leanne_T]

Morning @Maxi74

Thanks for coming here. 

If you would like to make a payment for the add-on before your bill date, you can make a card payment. 

Please see our How do I pay my phone bill?, Help page for details. 

Leanne.