agiletortoise, 
I submitted an address change request to App Store Connect, wanting to use my PO Box prior to updating my DMA compliance info.
Got an email with a case # from a “no-reply" address saying I'd hear from them within two business days. That was 6 days ago.
No idea how to follow-up with them. No obvious way to reference that case # or contact info provided. 🤷♂️