Hi!
Here to help.
It seems like you have questions about contacts and phone numbers.
I can help.
Usually, contacts are stored locally on the phone's storage or in mail-accounts.
That said, in particular cases, senders may be able t hide their contact information; however, this does not limit the recipient from saving the number and adding their own information (eg; if you would call me now, as "unknown' but your number is visible, then I could list you as "Apple-Question" in my address-book!).
The only advice that I have left - I guess- is contact the carrier; keeo in mind; Depending on location / country ; privacy laws are in place.
Hope this helps;
kind regards,
RRD