Telstra gen 2 box

Hi all, I recently moved and switched from Telstra to Origin and choose to use the Telstra gen 2 that I had. The plan is with the download speed 50 Mbps. But it never reach that, highest speed is around 30 to 35 Mbps. Normally is around 10 to 25 Mbps (the moment I am writing this is only 6.91 Mbps download). And we call Origin and did some changing to the modern setting twice. But the internet speed is still not there. Should I buy the Origin modem or should I try to change some more setting?