Under the new system, regional branches will open from 9:30 am to 1 pm, with staff spending the rest of their day as call centre operators, serving customers from all over Australia.
The new trading hours at Victorian branches are scheduled to take effect from October 4.
CBA's Australian-based contact centres are currently receiving more than one million customer inquiries a month.
Executive general manager of customer service network Mark Jones said the shift was an example of how CBA was adapting to "meet changing customers’ evolving needs" and "ensuring jobs stay in regional communities".
The announcement comes after dozens of regional CBA branches closed in 2021, including Goulburn Valley sites in Tatura, Leitchville and Finley.
CBA's Rochester branch and ATM will close on July 30, with customers encouraged to use branches in Kyabram and Echuca for in-person banking.
The branches chosen to reduce their operating hours will retain an ATM accessible to the community at all hours.
Affected customers "who prefer face-to-face banking services" are encouraged to use CBA's Bank@Post service via Australia Post.
“We understand these changes may be an adjustment for some of our customers, and the team at their local branch will continue to be available to help them find the solutions that best suit their needs,” Mr Jones said.