Is the salary earned from working at a telecommunications company that calculates late payment fees or installment benefits for customers considered unlawful, knowing that these benefits are not significantly large and that I cannot change the nature of my work? And what should I do?

Benefits from delay and what is analogous to them are usurious benefits (riba). The Prophet, peace and blessings be upon him, cursed the one who consumes usury, the one who feeds it, its scribe, and its two witnesses. It is not permissible to continue in this work if you cannot avoid recording these benefits, except in a dire necessity that prevents you from providing the necessities of life for yourself and those you support. In such a case, it is permissible to work until you find another job, as Allah Almighty says: "And He has detailed for you what He has forbidden you, except for that to which you are compelled." And a portion of your salary will be unlawful to the extent of your practice of recording these usurious benefits.