samsung SGH-A157 connectivity?

so ive got this old burner phone, its a samsung SGH-A157 but I noticed it had a micro-USB port instead of that proprietary one so I thought maybe it'd be possible to hook it up. I connect it to my macbook and instantly wwan recognizes it (OS X's built in cell modem thingmajig), i can open the tty on the command line with 'screen /dev/tty.wwan' and i can successfully interface with it through the AT command set. i know you generally cant straight connect a usb device to an arduino (mega 2560 in my case) without a host card, but i also know a lot of these crappy phones just use rs232 on the data pins. i thought before i go chopping a cable up, id see if anyone had any thoughts on this. i have some lm1488 drivers and receivers and a few max232's on the way. it does not have a regular headset jack, and i read you might can use a special cable for tty calls. cant seem to find a pin out though, guess thats why they call it proprietary. any ideas?