USB to iPhone question

Hey,
I have a 56 F-100 pickup with the original radio in it which was a very rare option(I say this because changing the radio is NOT an option.). I had the radio completely reworked and now has a USB connector for a USB stick. It seems it ONLY plays off USB sticks and not my iPhone when I plug it in through the USB port... is there anything anyone on here knows about maybe tricking it to think it's a USB stick and not my phone?

I believe the problem is with the iPhone and iOS itself. An android phone might be a better option for playing music.

I believe the problem is with the iPhone and iOS itself. An android phone might be a better option for playing music.

Used my brothers new android and one of his old ones with Spotify as well as saved music... seems to not only be exclusive to iOS.... any other suggestions? Is there an app that will make it as if my phone is just a storage device or some sort of thing I can purchase that will plug inline to trick it? Any suggestions are greatly appreciated!!

there are setting on your phone to make it look like a storage device