Azure SQL - Server login vs. database login
Your login is mapped to different database user, most probably to dbo . You can check this by executing:

SELECT CURRENT_USER


You can also compare the output from following views (and find matching SIDs to figure out login to user mapping):

SELECT *  FROM sys.sql_logins -- you need to execute this on master azure db

SELECT * FROM sys.database_principals -- you need to execute this on the database of interest