Assistant shouts at customer in front of everybody

When I got there after landing in Cape Town International I had such a struggle with the woman supposed to assist us. My friend tried to help out by sending her the email of my booking. The woman wrote down her email address on paper to send it to and my friend asked her to just check because Gmail wouldn't accept the email address. My friend, who is deaf, eventually tried to explain that the email address has got to be wrong because "mail delivery failed" notifications were received every time. The woman then shouted at her in front of everybody in the entire place insisting that nothing is wrong with the email address. It was shocking that a customer gets shouted at and it put a very sour note to our first day of vacation.