Moving Issues with Atnt --- seeing active line on property (already cancelled)

I've had major issues moving with ATNT Uverse internet/cable services. I've been told that there is an active line at my new address where I am renting. The previous tenant has cancelled Time Warner over a month ago and should have no active services on the property.

I share a building with 2 other units, however we all have our own addresses.

ATNT is adament that there is an active line, however we cant find the culprit. Any ideas?

Only thing coming to mind is my garage (which isnt shared with other units) has a black adapter with a coax cable running from an electrical socket into the wall and god knows where...

Could this have anything to do with ATNT seeing an active line on our account?

Thanks in advance for any help!

-Matt