Could Not Sign In The maximum number of free accounts have been activated on this iPhone.

Refer to If you see "The maximum number of free accounts have been activated" - Apple Support

To contact Apple:

Click here --> Choose your country or region - Official Apple Support Select your country, 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 --> "See a list of Apple phone numbers around the world."

Click here --> Contact Apple for support and service - Apple Support