There is of course the BFG of all questions:
"Why would you want to do that?"
Used properly (as in, as an answer to every fault report) you can delay dealing with the issue for weeks!
So you say that you have updated the file but the changes don't show when you refresh the page?
And you have purged the cache?
OK, can you try renaming the file and then refreshing it?
Why would you want to do that? Well just bear with me and try it
And you can still see exactly the same file when you refresh the browser
Can you double check that you have your FTP client pointing to the right site?
Yes, I thought that might be the case, have a nice day
https://en.wikipedia.org/wiki/Hello_Muddah,_Hello_Fadduh_(A_Letter_from_Camp)