Scammers are exploiting your "missed calls."
Someone with an unknown number calls. If you answer they hang up, otherwise you just see "missed call".
You call back to find out who it was, the scammers begin charging you for the call, and they make more money for each minute they can keep you on the line.
The Better Business Bureau says the "one ring" scam is on the rise.
Scammers use computers to call a bunch of numbers, and for every 99 people who never call back, at least 1 does.
Experts say the safest bet is not to return calls from numbers you don't recognize. You can always do a web search for the number and find out if it's a scam or not.