In order to use a Vodafone SIM card on Airtel dongle, you need to make the appropriate settings for this. You need to manually set the APN and the access number for the Vodafone SIM. The APN that is used in Vodafone network is WWW. To set it, go under Tools > Option > Profile Management > select New > enter Service Provider Name into Profile name > Select Static > APN and press the Save button. The access number is *99#, and in order to connect, you don't need an username nor a password so you should let the spaces blank.