Is it permissible for a person not to repay the remaining amount of the loan owed to the parent company, considering this as part of his financial rights and unfulfilled promises from the company owner, especially after three years have passed without the loan being demanded?

It is permissible to deduct entitlements from the debt amount if there is proof of the right; otherwise, there is a difference of opinion. The borrower is obligated to pay only the principal amount of the loan, without any usurious interest, as Allah Almighty says: "O you who have believed, fear Allah and give up what remains [due to you] of interest, if you should be believers" and "And if you repent, you may have your principal – [thus] you do no wrong, nor are you wronged." If the borrower is in straitened circumstances, he should be granted a respite until a time of ease, and it is better to give charity by waiving the debt, as Allah Almighty says: "And if there is one in [financial] difficulty, then [let there be] postponement until [a time of] ease. But if you give [it in charity] as a charity, it is better for you, if you only knew." What the company owner did by selling the employee to another company is invalid, and the employee may transfer with his consent.