My ISP has been playing the same game with me for months. I finally cancelled the contract when it was about to renew, and I got a very interesting winback call from sales:

Not only did the rep freely share the utilization numbers with me (80% during the day and 90% at night), he also mentioned that things would not get better until end of the year when they would do a node split.

As consolation, they offered me 10x the download speed for half the price. I'm not really sure how that would help congestion...