Do you have plans to travel to another country? You must plan ahead and find out if you need an entry visa. Failure to have the appropriate entry visa for entry or for transit to another country will result in denial of entry into that country!
It appears that there may be a resurgence of phone scams targeting international students or scholars in the U.S. The Scammers and the caller ID may identify themselves as U.S. Immigration or FBI employees or IRS agents. They may even alter their caller ID to appear to be coming from a legitimate government number.