International Call Scam & Spurious AT&T Fees

I've been getting a ton of missed calls from various countries overnight for about the last month and a half. These are numbers in the '+111 1 11 11 11 11' format listed as coming from places like Morocco, Haiti, Serbia, etc. Apparently, it's a scam that involves the scammer calling from another country, hanging up as soon as they can after the phone rings, and hoping people call them back. Somehow, they get a portion of the insanely high outgoing international call rates, so now there are hundreds of people doing this to try to dupe people who fall for it. I made the mistake early on of calling one back the morning I had a new employee from China starting, thinking it might be her, and stayed on just over a minute trying to hear the person on the other line. It was after this that 30-40 calls would start coming in overnight every night, and I found a $22.98 charge on my bill for the call.

Calling AT&T Customer Service was super aggravating, too. I explained the scam the same way as I did here, but they went off on a long monologue about how it's people calling pretending to be AT&T to get my account information (which it clearly isn't; I'm familiar with phishing scams). They said they couldn't turn off my international calling when I asked, and sent information about Call Protect and MobileSecurity, which I already have. So the call produced no results toward refunding the scam charge or stopping further attempts, and then I got an email saying I had a new $30 charge for "Device Purchase Without Commitment", which makes no sense and is apparently going to bring my bill up to $165.15.

Does anybody have experience with this, know how to stop those calls, and/or know of the best way to reverse one or both of these charges? I've been with AT&T for over 10 years now, but it might be time for a change if things get worse when I reach out for help.