Insert and if it already exists update the columns SQL
INSERT INTO users (firstname, lastname, email, mobile) VALUES ('Karem', 'Parem', 'mail@mail.com', '123456789');

INSERT INTO users(firstname, lastname, email, mobile)
VALUES ('Karem', 'Parem', 'mail@mail.com', '123456789')
ON DUPLICATE KEY UPDATE
    firstname = 'Karem',
    lastname = 'Parem',
    email = 'mail@mail.com', -- you can probably omit this
    mobile = '123456789'