I can't use the functions that have the fill command in them

I am not sure why this is happening but I create a new document in text edit on my mac then write valid fill commands then re name the extension mcfunction then turn into mcpack export to the game on my iPhone,then when I type and the function it says that the fill command has been executed but no blocks have been placed, all the other function packs I have downloaded have worked, I am not sure why this doesn't work but I will drop a simple mcpack and you try it and it won't work but if it does its a problem with my phone

if anyone could tell me how to fix this it would be great or it might be a bug