Lot of MacBook Pro users reported this issue. After upgrading MacBook from Mavericks to OS X Yosemite, Airtel 3G dongle not working. I am using Huawei E173.
Why this problem occured?
According to Apple support guide, in order to run modem you need 32 bit operating system. But OS X Yosemite is 64 bit.
Go to Huawei website. Download and install new compitable driver for your device. Huawei E173 driver.rar.
Open the .rar (archive) file. It have 2 files. User guide.docx and Mobile Partner.zip.
Open the Mobile Partner.zip file. It have Mobile Partner.app file. Double click the file to install the app.
After installed, run the app and go to Tools -> Options.
In the Options windows left side, select “Profile Management”.
Press the “New” button to create a new profile. Provide a profile name like “airtel 3g”. Also provide “Access Number” to *99#. Press “Save”, then “OK”.
Connect your Airtel Dongle to computer USB port. Run the “Mobile Parter” application. The the profile you already created like “airtel 3g”. Click the “Connect” button.