[Matite]

You need a collision file (COL). The COL file tells GTASA (and SAMP) which parts of your model are solid.

I can tell by the text you posted you took my iPhone model from the GamerX IMG... that is ok with me, my models are free for all to use but you really should of gone to my forum for help with this matter.

Anyway, you need this file too:
http://www.gamerxserver.com/downloads/iPhone.col

Merry Xmas.