What you're not hearing is called the "ringback". Call your carrier, tell them you'd like the number for engineering, to report a missing ringback. Your carrier generates that tone to send to you to let you know that it got a signal from the other end that the call went through. If they lost their ringback generator they have a big problem. This isn't the day of "pull out the old one and plug in a new one", this is the day of
the computer is doing something I won't mention on a family forum, and in a big way.
(You may have to work your way up through the supervisor, level 2 supervisor, head of tech support, etc. But each time, just tell them that you're trying to report a missing ringback. If they ask what that means, tell them "If you have to ask that question, there's nothing you can do to fix it, so please connect me with your supervisor."
This isn't a joke. When a few more stages go out, no one in your area has cell service any more. Someone at Verizon thought it was a joke about 15 years ago. It took about 14 hours to get that area code back on the network. (And it took him months to find another job.) One very large metro area lost a few billion dollars that day because without being able to make a phone call you just can't conduct business these days. (BTW, if your cell service for the wrong carrier goes out, in a large metro area, half your police and fire departments go deaf. A LOT of emergency coms these days are conducted by cell.)