What is the ruling on someone who hears a will between a person and God, and has witnesses to it, but does not act upon it and claims that the testator did not intend that?

The guardian is entrusted with what has been bequeathed to him, and his word is originally accepted unless contradicted by reality. The guardian's word is accepted regarding what he spends on the orphan if it conforms to custom. However, if he claims more than that, his word is not accepted. The guardian must implement a just will, for Allah has warned those who alter a will by saying: "Then whoever alters it after he has heard it – the sin is only upon those who alter it. Indeed, Allah is Hearing and Knowing." A detailed answer cannot be provided without knowing all the details.