Using Modem With any SIM Card Without Unlocking:

Here is a trick for your modem,

If you use UBUNTU,
you can easily access any SIM with any of modem which allows you to access SIM of any specific service provider.
The only thing you have to know is APN of service provider which you want to access.
Here are APN of some popular service provider:

• Airtel-                 airtelgprs.com
• Vodafone-           www
• Idea-                   internet
• Tata Docomo-     tata.docomo.internet

Either you can get the APN by calling your respective customer care.