[squill]

i can not turn off mass storage mode. How do I do this?

I am trying to transfer a pdf file and excel file but it will not work.

[jeffreii]

If you're trying to transfer a file why are you trying to turn it off?

When you plug the phone in to your computer it will pop up and ask you:

USB Drive
Media Sync
Charge Only

If you choose USB Drive it will enable mass storage mode. Charge only won't - it will "charge only".