Thank you for the answer.
My Blackberry is 16MB model.
I have upgraded it to Sw Ver.4.0 and I have configured the rigth APN in the TCP/IP menu.
I have istalled Verichat, Emailviewer Corporate ed. and Webviewer Corporate ed. and they works very fine on a GPRS network without BES/MDS.
After the upgrade the BB doesn't lock to specific network, and I can use it with Vodafone, Wind or Tim carrier.
Thank you for your support!