Guys, it looks like this is an unofficial TekSavvy (but official for other third party ISP) rule. Look at Acanac "DSL packages Overview". This is exactly what we are seeing every evening!
The problem is that TekSavvy never mentioned it. Is it a kind of fraud?
No, it is not an unofficial TekSavvy policy.
You were never guaranteed any particular speed at any time. Try actually reading the terms of service for any ISP.