Our internet has become really slow in the last few days (0.73Mbps tops). It was never very good, but it has become so poor lately that we got our telco (Telstra) to send out a technician to test our line. Before he came we took our modem to a friend's house and checked that it worked with a wireless dvice there, and it was fine. The technician came out and he connected his computer directly to the internet and he got 3+Mbs so it was not the line that was at fault. We found while he was there, that if we did not have the wifi turned on, our computers worked fine. He said there was a problem with a one of the mobile devices that must have a virus, or a program running in the background using the bandwidth. When he left, we tried to turn on the wifi on the modem, but even with with all our devices turned off the internet slows down including those computers on cable to the above 0.73Mbs. It seems just turning the modem's wifi on slows the flow of data. Because of this we thought this must be a modem problem, so we bought a new one. This one behaves exactly the same or even worse than the old one, as now not even the cabled computers work quickly even with the wifi switched off. So far we have spent $130 on a telco technician and $200 on a new good modem and still the problem persists. As we are a business that runs on the internet, this is a disaster for us. We don't know who else to get in to fix it or if there is anything we can do to fix it ourselves. Any ideas please?