Paying your bills in Japan is relatively painless, even if you can’t speak or read Japanese.
Paying with a credit card still isn’t that common, so the ones that do offer credit card payment are specifically gaijin friendly. Telephone and internet banking is common here but of course that doesn’t help those of us that can’t speak or read Japanese.
So the other option is to pay at your local convenience store, or combini. You can tell if your bill can be paid at the convenience store because there will be pictures of the shop logos printed usually on the back of the bill.
Take your bill to the convenience store, the clerk will scan it and tell you how much you need to pay. Or, show you the amount on the register, if you haven’t gotten the hang of numbers in Japanese.