Telstra experienced an issue earlier on Tuesday that prevented customers from making or receiving voice calls over its mobile network for about two-and-a-half hours.
The telco acknowledged the issues just after 7.30am, which it attributed to an unspecified problem "that occurred overnight".
Triple Zero and mobile data services were not affected.
The telco deployed engineers to work "urgently” to fix the issues.
By 8.30am, Telstra said the “majority” of impacted customers were based in either NSW or Queensland, and the telco said at 10.05am that a fix had been made, though some customers still reported some residual problems.
During the outage, Telstra had suggested switching airplane mode on and off as a potential workaround, noting that could "fix the issue for some customers”.
Alternatively, it suggested customers use wi-fi calling or an over-the-top, data-based service.
