Total scam. IF you call back may ask for your SS# to "verify" it's you. Sometimes they only ask for the last 4 digits making you think that's secure way of asking but it's complete BS.
OR more likely...
The call back number they give you is toll call number. For example... in the BVI - Bahamas and the area code 809. DO NOT call that back. It's very similar to the 900 numbers in the states but they charge a HUGE amount per minute. I'm talk over $2k per minute! Seriously... They won't ask you for any specific vital info so you think it's rather legit... BUT their goal is to keep you on the phone as long as possible... a 10 minute call will be billed to your phone for the tune of $20,000.00!!
Other area code are susceptible to this also. Why the Bahamas? Because they don't have the same legal hoops to jump through that safe guard the caller and still look like it could be from the USA. They don't have to tell you you're being charged per minute like this. Also, not all number is the area code are toll numbers so to make a blanket claim that all 809 area codes are toll scams is not accurate.
Either way just ignore it....