bluetooth issues

Hi everyone. I'm at my wit's end. I have this issue with bluetooth where I'll be on a call and if I get a notification on my phone (not everytime), I get major crackling that both I and the person I'm talking to can hear. It only stops if I switch to speakerphone or regular phone and then switch back. This happens in the car and on my headphones. I've done the following to try to fix it:

Replaced the phone

Switched service providers

Reset the phone

Set up my phone as a new iphone

Replaced the airpods

Switched to bose over the hear headphones

None of it helps. It happens constantly and I use this phone for work. The apple store has no clue and says my bluetooth on the phone is working fine. Any suggestions? I'm at a loss and beyond frustrated.