high frequent whistling / squeaked

Once the phone is connected, you can hear a high-pitched tone frequenting / squeaked. My colleagues have the high frequent whistling / squeaked heard. A senior colleague did not hear it, but he has also said that he does not hear higher tones.

I tested the phone on multiple ports. eg DTAG NT or Fritzbox 6360 and 7390. Here there is a manufacturing defect. I ordered this phone in my company, there was the high frequent whistling / squeaked also. My company has let the phone now for the 2nd time exchange over the manufacturer VTECH.

I always get a new and original packed device. With the phone what I ordered on Amazon, I had 4 phones in hand and with all 4 the problem was.

A request to Amazon: they test out the current supply a few phones.