We have AT&T & got the same call. Doesn't matter who your phone carrier is. These scammers and robocallers use autodialers that can dial hundreds of random numbers at the same time, and connect to anyone who picks up. They automatically disconnect when a voicemail picks up their call (except for the illegal IRS scammers and illegal "Litigation pending" scammers, who leave a recorded message on voicemail to frighten people into calling them back) or if they are connected with another number before yours.
Once YOU pick up, you will either get hung up on automatically if they are on the line with anyone who picked up before you, or you will hear a "bloop" tone and be connected with a call center filled with stooges who get paid to swindle you out of your cash or identity or property...or all three, or to insult you and make your life hell if you are smart enough to not fall for their sh_t.
What I do is NEVER answer calls from names or numbers I don't immediately recognize in the caller ID, and then I look their number up here at 800notes. I've done the footwork and called back most of these numbers, to save YOU the hassle, since I get around 5-10 of these nuisance calls DAILY, and 98% of them are spoofed numbers that are either "disconnected or not in service," or "the person you are calling is unavailable," or "voicemail is full," or some other BS that you can't get through to leave them a nasty-gram message. A few will give you a recorded message that allows you to dial a number to be removed from their call list, but be aware that if you call back, your number is recorded and they WILL sell it to another third party to keep making money off your number and get some NEW a-hole to bother you.
For those of you who can afford it, GET A CALL BLOCKING DEVICE. Call blocking services from your carrier or landline phone can only block so many numbers, usually 50-250 numbers. There are devices available that can block a lot more numbers, and believe me, there are that many telemarketing numbers and scam artists out there that you may need to block at least 1000.
Here is an easy remedy for those of you with a "dumb phone" landline, like me. If 800notes identifies the number as a scammer or telemarketer, I go into my "missed calls" list and SAVE the number in my phone address book under the caller ID name EFFING SCAMMER or AS$HOLE TELMKTER. You may want to use a more polite name for it, but I prefer to use strong language because that's just how I feel about these demon tormenters. Maybe use 0000 or IGNORE or any other name you wish so you can immediately recognize it as a bad call without having to pick it up. I save it because my call blocker is full and I can't add any more numbers to it. This way, whenever their ES or AT caller ID name shows up I know to ignore it and say a prayer asking forgiveness for my murderous thoughts against these jerks. There are literally dozens of different numbers in my phone under those names now. Let it RING! Or, pick up/HANG UP if you can't stand the ringing. Don't get all emotional about it...just beat 'em at their own game. Bwahahaha....