I did a certain quest about two guys harassing a woman. But I still encounter them. Is there any way to stop this encounter from occuring?

What? In My Time of Need?

You can check the quest page to see if its a bug, and how to fix it:

http://www.uesp.net/wiki/Skyrim:In_My_Time_Of_Need

Nope. Everyone gets it.

It's another one of those buggy quests. You need to complete it in a specific way to get rid of all the Hamerfell bros.