1) There is in fact an issue (reported below) with the software for this data card. I am on Mac OS X 10.10.3 (Yosemite). BSNL and Teracom who own the responsibility for India won't be able to do anything. Original provider Link Top needs to update the driver / software for this data card which they refer to as U302. I wrote to them on the product page http://linktop.appliances-china.com/Product_Look.php?ProID=136758 . Don't expect a reply because they deal with bulk orders and may not have a sense of end users like us.
2) I also tried to set up the "data card instance" that gets added automatically to 'Network preferences' when we run the install software residing on the USB data card. I set up the Telephone number to *99# and under 'Advanced' dialogue box set Vendor, Model, APN to Generic, GPRS and bsnlnet respectively. The connection once established immediately gets terminated.
3) To check the cause behind the issue, open a terminal and run the below command which effectively runs the installed s/w
arch -i386 /Applications/BSNL\ 3G.app/Contents/MacOS/BSNL\ 3G
Amid the verbose output produced you will see the below line
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '_setFrameworkScaleFactor called with non-nil _borderView'
4) Alternatively open Console app, go to all messages, click on clear display and then run the BSNL 3G app from Finder or Spot light search.
You will see the same uncaught exception as reported in (3)
Better to go for a new card as 4G is going to be a reality at least with Airtel and few others if not BSNL :-)