Lets say a company stores information in Catagory 1 , 2 , 3 .Catagory 1 in formation is assciated with email , Cata gory 2 with user name and catagory 3 with phone number.A user sends a request via email and writes "give (the user) a copy of the data." Does the company send only catagory 1 data or ask for more information and send more data for catagory 2 and 3?
Interpreting Art. 15 GDPR "Right of access by the data subject" I would think that the company in your scenario has to send all data which they have collected about the user, after the user is identified by e.g. email address. Plus other information like e.g. the purposes of the processing, see all bullet points in the link.
Is one possible scenario you think of e.g. having a newsletter based on email addresses, and, independently a webform where one can give name and phone-number?