What is the ruling on working for a company that maintains household appliances if the technicians receive large sums of money that the questioner feels are unjust, and is his earning considered lawful?

If both parties (the company and the client) agree on the quantity and quality of maintenance, and the amount of the fee, and the required maintenance is completed, then the fee is permissible. Workers should estimate the fee based on the cost of the work and a reasonable profit, to ease matters for their brothers and in compliance with the Prophet's (peace be upon him) saying: "May Allah have mercy on a man who is lenient when he sells, when he buys, and when he demands his rights."