As an HR expert, I understand your frustration with the reason given for denying your request for a salary increase. While it is true that the tasks you are currently handling may be perceived as simple and easily replaceable, it is also important to consider the value you bring to the company. Your willingness to take on additional responsibilities, work diligently, and adapt to various tasks should be recognized and rewarded. It may be helpful to have a discussion with your supervisor to further explain the impact of your work and discuss potential avenues for career growth and development within the company. Remember to also highlight any achievements or improvements you have made during your time with the company to demonstrate your commitment and value as an employee.