Optus has scored $100 million for the coffers of its new parent, Singapore Telecommunications' (SingTel) subsidiary SingTel Australia Investment, following a deal with St George Bank.
Subject to finalisation of contract terms, the three-year deal sees the telco become the sole telecommunications provider to the bank.
Optus will now manage its voice, data and mobile communications.
John Loebenstein, chief information officer for St George, said the company had evaluated its existing telecommunications providers - which included Optus and Telstra, among others - and had decided that dealing with multiple communications suppliers was not the "best way to ensure shareholder value and business efficiency".
"The deal will deliver substantial cost reductions to all St George business divisions over the three-year term," he said.
A spokesperson for St George declined to comment on a dollar figure for the expected cost savings.