The heater only blows cold air what can I do to fix it?

What is your question?

I have replaced the thermostat but it didn't help. I released the air out of the line and have a new blower motor but the fan works fine. Could there be a blockage I don't know about?

What makes this problem better or worse?

Nothing

How long has your 2006 Pontiac Torrent had this problem?

Maybe a year