Stop calling me!

Received a call while driving and there was no one on the other end.  The Caller ID indicates that the origination is in Canada.  I do know that a lot of fraud is now coming out of Canada, targeting people here in the US.  The most often used is by mail and includes a large check that is drawn under a legitimate company name and a phone number in Canada to call to inquire how to get the money... which involves sending money to them for "taxes" on the "winnings"...Though I have tried to "Call Block" this number through ATT, the service will not allow me to do so!

i didn't answer the call.  It appeared they left a message, but when I went to listen to my messages, there was nothing.  just a blank.

didn't answer when i picked up.  afterwards,  i accidentally pressed to the number to call back.  turns out, they're some sort of loan modification co.

After pick up the phone no talks, When I called back says mesage box is full. so, so aggravating!@#$%^&*

Received this call 2 days in a row.  Yesterday i pressed one to talk to somebody, told them I'm on the Do Not Call list and they promptly hung-up.

Today, i pressed one again, when I inquired as to their company name they promptly hung up again.

Very dishonest to say the least.  Not sure what action I can take with no information.