Android users with an Optus account may have just made games, apps, music, and books purchases even easier, as you can now charge the payments to your mobile plans.

Expected to be rolled out by the middle of this week, Optus has teamed up with Google to make it possible to charge your account for a purchase on its network, meaning when you buy an app, game, movie, magazine, book, song, album, or TV show using Google’s Play services, provided you have a post-paid account, you won’t necessarily have to pay for the selection until your bill arrives.

“We’re making it hassle-free for our Android customers,” said Ben White, Vice President of Mobile Marketing at Optus, adding that “there’s no need to store a credit card or worry about paying multiple bills, so [customers] don’t have to waste time before starting their next game of Angry Birds or buying extra lives in Candy Crush Saga.”

“We’re helping prevent bill shock by giving customers control to set up spend limits or add a pin for more security,” said White. “Plus, people are protected from accidental or change of mind purchases with a 15 minute window for cancellations.”

Optus joins Telstra in this move, with the big T having Android billing for some time, which has made it possible for customers to charge purchases to the dollars on their plan.

The good news is that there’s a limit of $200 per month spent this way for Optus, with a maximum of $50 per transaction, so even if you decide to use your bill to add more dollars or coins or diamonds to a freemium game, at least you’ll be cut off before you rack up a big bill.

We’ve tested it on Telstra previously, and found that purchases can be spent on the amount charged out of your card (the hard $30 or $40) and not the amount the cap value apparently translated to (the $200 and $400 values you get in return).

This means that if you spend $30 and get $300 of value, but buy a $5 game, that $5 will come out of the $30 you’ve added to your account. If it’s a post-paid account, you may find that $5 added to your bill at the end of the month.

On Optus, the service is currently only being rolled out to post-paid customers first, though we are checking with representatives for the telco as to when it plans on delivering the service to pre-paid customers as well.