question

ok he was making the purchases through a store which is why the vc prices werent there. I think the thing he was buying was 400-500 scrap [SC] he was doing things fairly quickly (approx 10 sec per purchase). I was on voice chat with him at the time and he started laughing saying that it was letting him keep purchasing after he had negative currency. When i tried to look at his profile i got a "Trouble loading profile" error message. I am using the following to make the purchase.
PlayFabClientAPI.PurchaseItem(new PurchaseItemRequest()
{
ItemId = ItemName.text,
StoreId = "MainShop",
VirtualCurrency = "SC",
Price = int.Parse(ScrapPrice.text)
}, OnVCPurchase, OnPlayfabError);

Do you mind if I create a profile in your title, to do some testing? This does not reproduce in my test title, regardless of whether I use a Catalog price or a Store price.

go for it. The whole situation seemed weird, with the whole profile becoming unavailable while it was happening. I added some checks on my end before it ever calls to make the purchase, but it was definitely getting the updated information from playfab saying his current vc balance was negative when he was still making purchases.

Sorry, but it doesn't reproduce in your title, either. I granted 10,000 Scrap to the account, then purchased an item from the Shop that cost 4,000 Scrap. I didn't wait as long as your tester - only a second or two, then purchased it again. On the third PurchaseItem call (again after only a couple of seconds), I got the expected "Insufficient Funds" error.

If you can reproduce this, can you provide a detailed step-by-step?

seems like it was just a one time glitch then hmm. I added some more code to check on my side just in case

it happened again, but only to -1700 this time. 

Could you please provide the repro steps, so that we can try this on our side - specific items, balances, etc.?

This issue occurred in my game.

By default 1000 virtual currency is granted for each user.

I've looked at the purchases history of that account and I've found 3 purchases with 2 seconds difference between each -100, -1000 and -100.

so now the user has -200 balance.

@Brendan let me know how I can help to identify the root cause of this.

Thanks, Hamza. The problem in this case appears to be that the client isn't waiting on the response from the previous call before making the subsequent ones. So, when call 1 (to subtract 100) was issued the balance was 1000. But since the client didn't wait for completion, when call 2 came in (to subtract 1000), call 1 wasn't done, and the balance still looked like 1000. When call 3 came in (100 more), it looked like 900 (call 1 was done, but not 2), and so it also ran.