strange robocall, when I pick it up all I get is dead silence then 20 minutes of what sounds to be random tones from numbers being pushed. I tried to hang up the line repeatedly but it would not disconnect for roughly 20 minutes.

No idea who is doing this, but even for a telemarketer it is a pretty stupid and ineffective approach to trying to steal people's money.

still getting calls from this number, mostly dead air, but occasionally I get heavy breathing and muffled sounds of someone handling the headset.

worst telemarketer ever.

dead air robocalls from this number - ties up line for several minutes

dead air robocalls from this spoofed number