my internet is fine, but my cham just lagging so much !

my internet is fine, and i was playing jinx, but i couldnt change my q, and everying just start lagging, and i thought its my pc's problem, so i changed to another pc. and its still the same. i just wanna know what can i do ?, because i can leave game , and comeback , with like 70pings, but i just couldnt play the game. wont let me undo, wont let me type to my teammate . why is then happending to me ...... and of course , that was a rank game .....