If you can't log in here
https://my.boostpower.co.uk/login
and you've not got a smart phone, you can top up your account with your payment card at any PayPoint
https://consumer.paypoint.com/
(If you're experiencing problems with logging into my first link above, try using the 'Reset my password' link there. Otherwise call 0330 102 7517, Mon-Fri 0800-1800 or 0900-1300 Sat, for help in getting things sorted out. Calls are charged at the same rate as for 01 or 02 numbers; if you've got spare 'included minutes' on your call plan, that will make it a free call).