By Byron Kaye

SYDNEY For one talkback radio caller, the first sign something was wrong with Australia's second-largest internet provider, Optus, came when her cat's wifi-powered food dispenser failed to serve breakfast at 6:10 a.m. and her pet woke her.

For disability pensioner Chris Rogers, who needs painkillers for a knee injury that prevents him from working, the problem became apparent when he drove 30 minutes to the pharmacist and his electronic prescription could not be filled.

"Because of the outage it won't load," Rogers told Reuters while he was waiting at the pharmacist for the internet to return. "Reception is flat out. It's crazy, I've never seen such chaos."

For millions of Australians who could not pay for goods, book rides, get medical care or even make phone calls, a nine-hour near-total service blackout from the company which provides 40% of the country's internet became a lesson in the risks of a society that has moved almost entirely online.

In the three years to 2022, Australian cash transactions halved to 16% as pandemic restrictions sped up a longer-term trend toward so-called contactless payments, according to the Reserve Bank of Australia. One-quarter of the country's doctor appointments are online or by phone, government data shows.

"We are now so very reliant, because of COVID, on telehealth and also electronic messaging systems," said Michael Clements, rural chair of the Royal Australian College of General Practitioners.

"The reality is many people have just missed out on care."

Optus, which is owned by Singapore Telecommunications, gave no explanation for the outage except to say it was investigating it. Most of its services were restored by the afternoon.

Until then, even taking a walk became more difficult, at least for people who needed directions.

"I'm looking for a bank, and when you can't go onto your phone and Google pretty much you are lost," said Angela Ican, a security officer in Sydney's central business district.

An office worker from Sydney told Reuters he could not get into his building because the door required an internet-connected smartphone application to unlock.

Small businesses owners told Reuters they either relied on regular customers to pay them back once internet was restored, or gave customers an option to pay cash or come back later.

"We are a A$4,000-A$5,000 ($2,600-$3,200) a day business and we've lost about A$1,000 in coffee sales this morning," said Roderick Geddes, owner of Pirrama Park Kiosk in Sydney, which was unable to process electronic payments.

($1 = 1.5538 Australian dollars)

(Reporting by Byron Kaye with additional reporting by Kirsty Needham and Sam Holmes; Editing by Stephen Coates)