Is the warranty considered a gift from the company that the buyer has the right to benefit from without returning its value, or is the aforementioned action considered an encroachment on the company's funds, necessitating their return? And if a return is due, what is the method for doing so, and what is the intention behind the donation? And is one sinful for refusing to help their family in returning the amount?

It is permissible to sell a product with a warranty, and any defect occurring after the buyer takes possession of the sold item is the buyer's responsibility, unless there is an explicit text from the manufacturer or similar entity stating otherwise. It is permissible to benefit from the seller's warranty if they commit to it for marketing their product. However, the terms of the warranty must be adhered to. If deception is used against the company to obtain the warranty, the new device must be returned and the company compensated. If that is not possible, the value of the new device or a settlement must be paid. If it is impossible to deliver the value, it should be given as charity on their behalf. As for accepting help from family to pay off debt, it is not obligatory for you.