go over there: Is correct, and used when you tell somebody standing next to you to go somewhere further away.
come over there: Wrong... You can say come over here, if you want somebody to come to a place located next to you.
go there: is rather slang form for go over there;
go here: not English, not logical. You can say go there or yet better go over there
go over: Wrong... say: go over there.
come over: Wrong... say: come over here.
“please come to the line at the counter to pay”: This is fine in the sense that it's English, but not natural. I may say: You may pay at the counter over there (smiling, of course), or more politely, would you please pay at the counter over there.
Hope this helps...