You can send specific amounts for bill payments or just send zcash and let the site exchange it to equivalent BTC value.
This is a second topic. I addressed several privacy and trademark concerns that were brought up in the first one, in particular by @Shawn (thanks!) :
Email address has been removed from the form. This means you need to save your order id if you want to discuss the order with support (support email is on page)
The website is not ran by or associated with Electric Coin Company.
As with any non-atomic, centralised exchange, you need to trust me not to run away with the cash. (look up Mt. Gox). Unlike an exchange, I don’t hold on to your cash, so IMO the risk is lower.