GPRS AT-commands for Siemens cell phone

Question

I've a task - remote temperature monitoring. Hardware is atmega328 microcontroller, simple analog temperature sensor and old cell phone Siemens cx75 (this device has a GPRS module). So, I'm looking for AT commands to send some bytes of data via GPRS from this phone. There are many documents about GPRS commands, but I've found just for modems insteed of cell phones.
Maybe someone can help me? Or is it easier to use another solution?

UPDATE:
I've some progress:
First of all I set PDP context:

at+cgdcont=1,"ip","mts"  
OK  

Then

at+cgatt=1
OK

at+cgact=1
OK

It's ok, I've been attached to packet domain service and PDP context
So, what should I do next? I have tried some modem commands, such as

at+cipstart=0,"tcp","178.xxx.xxx.xxx","8001"

but I've got

ERROR

Answer 1

According to @S List 's link, there is no opportunity of gprs-connection using clear atmega328. It's seem the easiest way is to use GRPS-shield.