Serious Problem.

So guys since last week everytime at 20:00-21:00 o' clock,everyday I get from 69 ms to 1900 ms and only in League of Legends.Everything else works fine,other games or applications,youtube everything.My router is not going down so there is not a problem from the company working with to get my internet.Any ideas?That time around I have some free time to enjoy this game but since this is happening you can understand that is so sad.I tried to find something in the boards but nothing.

Any ideas?