Re-approved ACP & upgraded to Plus 12/7, now have a partial charge for 12/7-12/14?

This will be a bit terse, since the forum lost my detailed friendly post by forcing me to log in again, which is incredibly frustrating.

Here's the basics: I'm an existing Essentials / ACP customer, renewed on October 17th as it would expire on December 9th, the GetInternet site goofed and didn't apply it to my existing Xfinity account.  I called on December 7th, the person used the app ID to verify I qualified, then renewed and upgraded me to Essentials Plus as she said it wouldn't cost me anything.  The order confirmation also showed me not owing anything.  However, I got an email the other day informing me I'd be billed for "partial charges" of $5.16 for the week of 12/7 --12/14.  I'd appreciate it if somebody could help me fix this.