Is it possible to turn of the GSM radio and still use data connection? I recently starting using a Samsung Galaxy S4. I need to use a special phone at my work. For that purpose I have a duo card where I turn off one phone to use the other. 

The problem is that I can only turn off all connections on the Samsung (Airplane Mode), including the mobile internet connection. 

My question is: can I turn off the phone capabality (GSM?) on the Samsung while maintaining my mobile network on the Samsung?
Simply impossible. Mobile Network IS GSM. GPRS, EDGE, UMTS or LTE, which are different standards for providing packet-based Internet connections, are all expansion of the GSM standard and, as such, require a GSM signal.