First, you have to hunt where the birds wanna be, so set up where you see them when you are scouting. This might sound obvious, but ALOT of guys don' seem to get it; just because you wanna hunt a certain spot doesn't make the birds wanna go there. Figure out why the birds are where you see them.
I've had some success calling woodies, but they respond better to movement. I usually rig up a jerk cord to one decoy and use it among the rest. It works. You may be blowing the call right, but you might not be blowing it at the right times, or perhaps your cadence is off, or there may be another problem you might not be aware of. Do you have any experienced hunters you could get an honest opinion from?
There's a heavily hunted spot on the river not too far from me. The birds roost on some ponds where no hunting is allowed and fly out to feed in the mornings. These birds get shot at almost every morning as they leave the ponds, and guys hunt the river all the time, calling at every duck that comes in sight of them. These birds fly AWAY from loud calling. I've had considerable success hunting a puddle about 100yds off the river. I'll put out 4 or 5 decoys; one of them rigged to a cord, and only blow some low single quacks when birds come near. Once again, it works.
Good luck.