Can anyone help me to fix up the speed for my Optus internet.
I am paying for the 100mbps plan, but I only receive the speed between 4 to 5 mbps. Optus sent already its technicians and engineer 2 times. They also changed a new modem every time they came. They all beleive, there are too many optus users in the area (Putney area). In fact, I have the same speed from my TPG ADSL 2 I had prior to changing to Optus broadband.
what should I do now?
Unfortunatley there's no much else you can do.
For sure immeadiately stop paying for any speed boost (and request a refund on any months to date) - Optus sometimes offer to apply it for free in these circumstances anyway.
If the issue is the number of users in your area then you should see your speeds change over the day (80Mbps at 7am, 5Mbps at 7pm) ? Is this the case or are you at 5Mbps always?
Whether its congestion or just the cable network is not up to speed in your area is probably not really relevant though. Eitherway its unlikely to be fixable. The good news (and the reason its probably on its last legs) is that the NBN is in your area in February. At that time you'll be able to connect to a spanking new cable HFC network (Optus' is going to be junked) and you'll have many options about what to do then.
Sorry to not have a better answer
PS You can also end your contract with Optus for non performance if you like but as you say, where would you go to that was better?