My iTunes is set to manual sync, yet it still auto-syncs with my iPhone?

I checked the option to have my iPhone manually synced.

My iPhone is filled to capacity, but i want more music. So after checkng off the sync manually option, i deleted about 100 songs straight off my iPhone. Next time i plugged in my iphone to my computer a notification pops up telling me that "60 songs were unable to transfer," and the songs i tried transferring over didn't transfer. A bunch of song titles on my iPhone are now faded out, including those that I wanted to transfer but mostly were those songs that i deleted off my iPhone but were still in my iTunes, meaning they couldnt transfer due to a lack of space.

It's so annoying, please help. I've posted in Apple support forums and they hadnt answered. Thanks everyone

Added (1). Thanks a lot Andrea. The only way i want new songs added to my iphone is just by drag and drop from my itunes to my iphone. I just unchecked all my songs. Does this mean that if i sync, all my songs will be deleted off my phone though? Or am i safe?

Added (2). I don't want to tick/untick songs to manage my library on my iphone because i have 1000+ songs

Even if you choose to sync manually, itunes will still sync all songs that are ticked in your library. You need to untick all the songs in your library that you do not want to transfer to your phone. Then sync and any unwanted songs will be removed during sync. Manually deleting them from your phone won't remove them- everytime you sync they will come back but will be greyed out:

Tick all the songs you do want on your phone: Now sync: should resolve your issue:

if not edit the post: I will watch