Hi farhan.rashid,
Oh… I see what you mean now. I thought you renamed something else inside the htdocs folder. I tried to rename it just now and somehow it worked… This is definitely not normal as I have been on other hosting that does not allow this. Maybe here you can rename it at the risk of bringing down your website? I have no idea. I am astonished anyways, thanks for letting me know something to be aware of.