Are you sure that the points were debited twice? I doubt that and think it's probably a misunderstanding because of the way it's shown in your account view. They have started showing the points used for awards on the same date when your stay is posted, even though the points are debited on another date (normally at the time of booking but sometimes at another date).

For instance I have an award reservation that I made at the beginning of this year that I haven't completed yet. It's now showing in my account as: Jan 6 / PH xxxx / Award / -44.000. But after completing my stay that entry will vanish and will be replaced by two new entries, both dated the date of my stay (one showing credit for my Diamond amenity points and the other a debit for the award points). So it's just an adjustment of the date on the debit, not actually another debit entry.

It's fairly easy to check for yourself if you go to your account view, you don't need GP to do that.