More than 280,000 users are said to be affected by ispOne's move. The cut-price services had been offered by online retailer Kogan Technologies and supermarket chain Aldi, using the wholesale Telstra service provided via ispOne.
But those services were under threat of being cut off after the Federal Court on Monday dismissed a court case between ispOne and Telstra over allegedly unpaid bills. The court dissolved a court-mandated injunction stopping Telstra from cancelling the services.
IspOne is believed to have appointed the Ferrier Hodgson group as administrator.
Optus yesterday said it "is providing certainty for people who are unclear about their current mobile service with Kogan and Aldi, with a limited time offer for those who bring their number to Optus."
From 5pm yesterday it was offering users of these services an opportunity to switch to an Optus prepaid deal. Optus did not offer to match the low-cost deals offered by Aldi and Kogan, but - to sweeten the offer - said it would double data and standard talk provisions for the first three recharges of $30 or more.
Data provisions on offer range from 500MB on a $30 recharge to 5GB for $100.
Said Ben White, mobile marketing VP at Optus: "No-one likes uncertainty with their mobile service and we feel for people who are currently worrying about it. We're hoping to make things better by offering an easy way for you to come to Optus, keep your existing number and continue using your mobile service."
Telstra meanwhile said it had negotiated a deal with Aldi subsidiary Medion Australia which will see Aldi customers retain their service. But it would not accept any requests for new Kogan Mobile services via ispOne, although it said people with existing services would have the opportunity to switch to other providers.
"People who have services through ispOne and its retail partners, such as Kogan Mobile, are not customers of Telstra. We do not have their account information and we cannot provide them any customer service support," said Telstra wholesale group MD Stuart Lee.
A statement posted by Ruslan Kogan on the company's Web site said "We're devastated", by these events. "We set out with the aim to make mobile services in Australia more affordable for all, and were well on the way to achieving this goal."
The statement said Kogan is seeking to negotiate deals with several leading mobile phone providers. In the meantime it recommends that users transfer to another provider.