Who are they, they call all the time but I do not answer?

Two years ago, I told them not to call me and they didn't call me for a while.

But they just call me now Oct 19 2011, 19:30 and last week at evening as well.

This is University of Waterloo, trying to solicit Alumni donations.  They call fequently; we don't answer.

Someone called  me  last year  and  I  was not interested  in  donating any money.  She finally  got  me to  agree to  donate   $20.00.  I  figured I  would  ignore  it ,  but got  a  letter  thanking me for  my  future  donation .   I  became  really  angry  and  sent back an email saying I  thought  it  was  disgusting  them asking  for  money, when  they receive  thousands  of  dollars  from foreign  students. I  got a  very gracious  letter  back and they apologizedI am  on Long Term Disability  and I  chose  where to donate    my meagre amount  of  money.  They  just  phoned me tonight  and I  saw the  number  and didn't  a answer.  I  am  going  to  call them back to  take  my name  off the list.

About every night around 8 pm this number calls me.  When I answer then is no one there.  If I cancel the call, a voice message is left.  When I listen to the voice, there is nothing there.  If I just let the phone ring, there is no voice message.I really need these calls to stop!

they keep on calling me everyday around 6-7pm. does anyone knows how to block this phone no?