CREATE TYPE ContactNo from varchar(20) --CREATE USER-DEFINED DATA TYPE
--EXEC sp_addtype ContactNo, 'varchar(20)', 'NULL' --OR YOU CAN CREATE THROUGH SP
EXEC sp_rename 'ContactNo', 'ContactNumber', 'USERDATATYPE' --RENAME USER-DEFINED DATA TYPE
EXEC sp_droptype 'ContactNumber' --DROP USER-DEFINED DATA TYPE