blower in head mode on 2005 Chevrolet Trailblazer

blower still blows at feet when put in head/foot or head mode

This may be a problem with the motor actuators, or the system that controls them. If you are not familiar with these systems, get a good repair manual and read up on them, or take it to a shop so they can diagnose this problem.
1 more answer
Your diverter motor may be inoperative. It is a pain to remove. Sorry...