Hello ahmed;
Ask your local Siemens rep about the Micro-Automation Sets (MAS) and S7-200 bundles, they have a great solution for GPRS data collection.
To start off you research, look at the basic MAS 21 here; it is a combination of S7-200 CPUs, Sinaut wireless modems and Sinaut OPC communication software for GPRS support: https://www.automation.siemens.com/microset/html_76/solutions/mas21.htm?HTTPS=REDIR