what do i say when im being harassed ?

i just recently started a foreign exchange in grenoble, but i have encountered a lot of way older men who are harassing me for a date or my number/snapchat. i've tried ignoring them but that does not help. what is the most effective phrase to get them to leave me alone ? i've tried << ne me parlez pas >> but it hasn't been very helpful. any tips ? some polite, some not would be very helpful :)