To add to that, sometimes if you are at the far end (furthest from the VDSL cabinet) you may only get 2.5-5 Mbps download speed. It's just the nature of the technology. In these cases, if they were to override the auto detection and lock your box in at a higher sync rate, it may just experience high errors or dropped signal.
The classic tv box connects at one of three rates; 17, 20, or 26 Mbps, dependig on line conditions. The tv streams use 15 Mbps of that, so whatever is left will be used for Internet. Although they must limit it to 9, because at 26 there would theoretically be 11 left.
Sorry if that's too technical.
Authorized Service Provider (Contractor) for MTS Allstream. Any views expressed are my own.