My father pays for my PC but my grandmother paid for his apartment?

Hello, my father left for Kazakhstan and left me a deposit for my PC, but then there were additional costs for the apartment in which my father lived. The apartment was paid for with the money that was actually for the PC, but today it turns out that my grandmother paid the bill and I can afford a PC after all, but I don't know what to do, give the money back to my grandmother? My father also said that he will give the money back when we come to visit him. But my father is also in the former situation. What should I do?