Most people pay their bills at Magyar Posta, the Hungarian post office. Any bill that you get in the mail — gas, water, electricity, mobile phone, internet, etc. — follows a standard template. At the bottom, there’s a detachable section that you take to the post office to pay your bill.
There’s also an option to pay via mobile phone. I much prefer this option, because the post office often has long lines, and people there — though friendly — rarely speak English. To pay by phone, download the iCsekk app and fill out your credit card information. Then, to pay a bill, simply scan the QR code on the bottom (every bill has one) and follow the steps. With this method, paying bills literally takes about a minute each.