SLOW INTERNET

I am downloading a 324 MB file every second evening (anti-virus definitions file). I have noticed that when I am doing the download between 19:00 and around 21:30, the download takes about +- 1 hour (between 50 - 90kb/sec).

When I download the same file (and size) OUTSIDE of these hours, it takes about 5- 6 minutes ?

I am on a 10MB fibre line (MWEB / Telkom product).

WHY is this happening ? Maybe I should consider moving to another service provider with better service especially between those hours mentioned above.