I can't get past the html or php error message

I got this usual error message caused by saving a page as both of an html file and php file. It has been a while since I’ve had to deal with this but I remember selecting “delete html file” usually tended to work. Unfortunately I’m having difficulty logging in to my FTP program so I’m a bit stuck on what to do. Does anyone know why clicking “delete html file” doesn’t seem to work?