Iphone 5 on manual for music?

Every time I plug in my iphone, it resets my music preference from 'manual' to 'sync' which is Really annoying. If I want to change said setting, it says I have to erase all the music on my phone in order to set it to manual, only to have to do that EVERY TIME i plug in my iphone! Does anyone know how to keep the manual setting on? Or how to keep it from erasing everything?

Hmm