Sonic.NET landline noise problems

[http://dummy.us.eu.org/robert (Robert )]

We are having a few of problems with our Sonic.NET-based landline.

 1) For some numbers, callers cannot get through to our landline phone.  The
    landline phone rings and we pick up, but the line appears dead.
    Meanwhile, on the caller's end, the ringing continues forever.
 2) For other numbers, the caller can get through and we pick up the
    phone, but, on the caller's side, the ringing of the line continues
    during the call, making it difficult for the caller to hear.
 3) Calling out on our landline phone works fine, except that, even after
    the recipient (called person) answers the phone, ringing continue on
    their side, which, again, makes it difficult for them to hear us.

We would like these problems addressed.

Thanks.