Well you could block them, i think it stops them from commenting on your posts, or you could try and talk to them about it and mabey they stop

can you help like what should I do it's getting so frustrating.

I looked at your post and I think I can tell who it is

If you want their username check my latest anime.- it's annoying and they won't leave me alone

S a d. Also I'm being harassed by some random person who won't leave me alone after a full d a y. Just asking if you knew them?-