Meghbela Broadband Blocking Router MAC Address At Evening And Reducing Speed

[Ashim_]

I was facing low speed and packet loss at evening for several days. When i contact them they always asked me to connect without router directly ONU to PC.
After connect directly i face no issue. everything worked perfectly. They told me the problem with my router.
Every time i contact them they told me the same thing.

But the main problem was other than evening to 10 pm everything works perfectly. At the day time there are no speed issue or packet loss issue.
If problem with my router how there is no problem at day time.

LCO guy also told me if there are no packet loss from router this problem must be from ISP.

I was also thinking If my ISP (Meghbela Broadband) reducing speed intentionally for specific time by detecting MC Address?

So I just set a custom MAC Address on my Router hoping it will work. And it work perfectly.

Now no speed issue and packet loss at evening. Everything working perfectly.

I am just waiting when they are gonna block my this MAC address.

Why should any ISP thinking of doing that to there paying customer?
How it's even justified?
Is it normal to every ISP? Every ISP Do that?