GR Reversal in EWM

Hi EWM Gurus,

My Scenario, I completed my Unloading Task and after which GR is completed.

System created auto Putaway Task.

Now I want to reverse the GR. I cancelled the Putaway Task.

And tried GR Reversal its not happening.

Error: Delivery XX Item xx: Putaway WT created (cancellation/reversal not poss.)

Kindly let  me know how can I reverse the GR.

Thanks & Regards

Ramesh.R