Julie Cousin's heartfelt letter was shared by her proud son, Joe, wishing her a happy retirement.
He posted it online, explaining she had been cleaning banks for 35 years, and added "always having the last laugh eh!".
Julie wrote in her note: "Hi ladies, tomorrow will be my last clean for HSBC. I have made up a bucket of cleaning materials for the next cleaner whoever that may be!
"I've left the job after the way you dressed me down in the office.
"It was nothing more than aggressive and cruel but that's a reflection on your character, not mine.
"So going forward, please all of you remember: in a world when you can be anything, BE KIND.
"Because you are all no better than the cleaner."
Her words went viral, with people on Twitter connecting with the point she was making.
She was praised for being honest and explaining exactly why she was leaving.
Joe added on his tweet: "Yess! What a woman. No one is better than anyone else.
"I really hope this gets the attention it deserves because the bank needs to know lol.
"Good on her. Happy retirement."
One person commented: "Never understood why people think what they do for a living reflects their importance.
"I was raised to believe that a job is a job and anyone getting up and going to work deserves the same respect, whether they pick up trash or run the company. Good for your mom! Respect!"
Another added: "I remember reading about a firm who paid everyone the same, no matter what there job, as everyone was equally important. We could learn a lot from that.
"If you’ve got up, gone to work, worked hard, then no one should belittle anyone!"
Joe praised his mum for her note on her last day as a cleaner in that branch