It looks like Mate NBN is slowly auto-upgrading all their 'Good Mates 12/1' NBN plan users to the 'Great Mates 25/5' NBN plan for the same monthly price of $59. It means an upgrade from 10mbps download speed to 19mbps in typical busy period as per their website.
My account has already been moved recently and the speed increase is real. Couldn't be happier with a $59 plan :). Worth checking for the scheduled upgrade date for your account if you're curious. Looking at their website, I assume that it would be happening to all their 12/1 NBN accounts eventually.
Definitely worth a shout as people need more bang for the buck in these difficult times and internet is one of the most essential services at the moment.