Unfortunately you can only go by the speed the road allows.
In the early days when most isp and modem manufacturers where in early stages of adopting docsis standard, there were weaknesses in the implementation and people exploited that hence the rise of this ideas of getting more than you are paying for.
The modems used to dial and download a config file. It was that file which you could intercept and change value.
But the industry and isp are now wise. Im not saying there is totally nothing out there or maybe something new, but its not something l hav yet to come across