Advice on how to handle Schwab's mistake?

I am new to trading, and new to Schwab's platform. In July, I signed up for an account and received the $101 in stock slices that they offer as a promotion. To confirm, they give me $101, and then they use that to purchase the stock slices. That all happened as I expected.

I noticed this morning that the cash in my account had gone negative, but not because of any trades I made. Looking at the trade history on my account, they made the same $101 stock slice purchase again, but this time didn't put $101 in my account first. I chatted with support, and he confirmed...

So, what I am seeing is that there was a note on your account from yesterday, 9/11, stating that due to a backend issue, Starter Kit funds were not automatically invested, but that this issue was resolved. The "resolution" appears to have been that the investments were made today. However, you are correct that it appears the purchases were also made initially in July.

and...

It does look like your account ending in XXX has a negative cash balance of -$XXX. This leads me to believe your cash was used for this.

He advised me to reach out to the Trade Resolution team by phone. Clearly, I should not suffer repercussions (ie owed interest) for a mistake that they made. Any advice on what I should ask for from them to make it right? Also, I'm a bit freaked out that they just accidentally executed a trade on my account. Has anyone ever heard of this sort of thing happening before?