Double post all the way across the sky.
Now seriously - I bought a shitload of boosters when I only needed one because I'm an idiot.
I asked for a refund on the remaining boosters I had purchased - which factored out to 850 Kan (The 1k, 2500, and 5k Boosters)
I have asked repeatedly, and now I'm putting it here. I never got told if that refund ever went through. I would very much like to know.
Additionally, I somehow had a negative balance of Credits which I didn't know was possible in the first place. Does someone know how that might've happened, and if so, can you fix it? I was docked 28 points as a result when I withdrew my balance from the bank.
What might be a more effective way to ask would be to actually PM or IM the people who can check.
The Kan has now been refunded.
As for XP, which is what I assume you mean by Credits, it is sometimes slow to update how much you actually have and will allow you to buy things even if you don't actually have enough -- if you had enough a few minutes earlier. So, the negative amount was most likely legitimate.