Yes!!! And yeah I'm on at&t too...What is that?!?!?!
. I also have AT&T prepaid, Samsung Galaxy S9, I started getting this "beeop" sound couple months ago, it would happen randomly. On some calls it would happen, once,, other calls, all the time,, occasionally it would take the audio away.... I can give you the whole details of what I did to resolve this, undoing this, uninstalling that, change settings,, calling ATT support, calling Samsung support,,, I discovered what was happening on my own.
I have 2 devices paired & connected through settings/bluetooth, Samsung Gear Fitbit Pro 2 smartwatch and an old AT&T wireless/bluetooth 6.0 answering machine system with one wireless extension, the phone is approx 10 years old. When a call would come into my cell phone the 6.0 landline phone would ring as well in the house- I am hearing impaired so I needed that and I could answer the call using the 6.0. I turned off the call ability setting on my cell phone, still got the beeop.. I unpaired both devices,, nothing, I turned off the settings bluetooth, nothing.... so obviously it was one of those 2 devices, or so I thought, it ended up being both of them. I did a factory reset on the Smartwatch,,, and unplugged the 6.0, because leaving it on, the cell phone would keep scanning & tried to connect. I have had around 10 phone calls since doing that,,, and have not received the beeop/call interruption anymore. I am not totally sure what was happening, only to assume it may have started from the 6.0 phone possibly interfering with the RF on the smartwatch or smartphone and the cell phone could not understand which device to send the call to. I will probably go buy a new house phone.