How do I delete an alias to my Apple ID?
How do I delete an email address which is an alias to the Apple ID email address?
Trying to deal with @me.com addresses an be a bit challenging. I suggest you pose the issue to Apple itself:
Refer to this document for ways to contact Apple --> Choose your country or region - Official Apple Support
Select your country (also look for "other" regions), then a product. If you don't see one that handles your issue then keep experimenting with selections until you reach one that gets you a chat session or a telephone call and get the representative to redirect you.
or:
Contact Apple for support and service by telephone --> Contact Apple for support and service - Apple Support