topping up

[slippinjim]

whenever i go to top up, it just gets declined. even tho my card details are right and i have sufficient funds. 

[jonsie · Accepted solution]

Lots of info in this guide

Guide How to Top Up (PAYG) 

If this is the first top up it may need to be done by voucher

[pgn]

In addition to @jonsie's point about a voucher (or registration of your card), note that O2 won't accept Monzo or Revolut (among others) cards as valid payment methods.

The most excellent guide @jonsie shared was updated recently to refresh this and some other info in there.

Good luck, @slippinjim