[H] google voice

[Winterlight]

I have my Goggle voice number forwarded to my AT&T cell phone. 
Unanswered Google calls would be picked up by Google voice mail box 
and unanswered AT&T calls would be picked up by my AT&T voice mail. 
But somehow that changed, and unbeknownst to me Goggle voice started 
picking up all the calls. I didn't even know I had messages until I 
looked in my Gmail account. How do I deactivate Google from answering 
my AT&T calls.