We recently moved to a new place and got ADSL2+ hooked up 3 months ago as NBN isn't available yet. The problem is that when I am streaming Netflix it works, but if I add another device it slows down. If I turn Netflix off and just browse on a phone it is really slow and struggles to load pages. I've been in contact with Optus on three occasions with no resolve, so this is my last resort before I tell them to shove their broadband.
Based on your description the issue would appear likely to be the in home setup.
Its a bit hard to work out what your tests are showing:
1. Is any connection over wired?
2. Is the Phone over wifi?
3. Do you have a PC in the mix to test on?
4. What sort of speeds are you getting when you run a speed test (try the optus speed test and another site speedtest)
Ok so with my laptop connected to the modem via the supplied cable the highest speed is 5.1mpbs and lowest 4.7mpbs. Connected through wifi top speed is 4.1mpbs and lowest 2.5mpbs.
I was on the phone with support this morning and a he did a few things on his end and now I'm getting buffering every 5min when im streaming. He also said that these speed should be right as im 2.5km from the exchange, which I think is crap because 2 years ago I wasn't having these problems. I'm really sorry now that I canceled the vivid wireless for the crap service. A technician was sent out last month and was told that the in home setup is right.