High pitch noise when retrieving VM Voip

People are leaving VM on my Voip line.  Many times when I retrieve my VM, I hear a high pitched noise, and I think the message in the background I cannot understand the message through the noise.

It does not happen on every call,  but probably about a quarter of the time 

It does not matter where or what device.  Even visual vm cannot transcribe.

Who do I contact to resolve this issue.