cancellation of a verbal agreement

Good day! i rented a boarding house for my cousin visiting here in Iloilo. He is from Davao. i paid the full amount agreed between me and the owner of the said boarding house. i rented the place for 1 month, P1,500. i paid the full amount before my cousin arrived. When he arrived here, my uncle on the other side of my family decided to let him stay to his house, we are trying now to cancel the room that we rented. i did not sign any contracts and the owner did not give me any receipt for the amount that i paid. now, they are making excuses when we tried to get a refund for the room since we will not be able to use it. we did not even use it by the way. what is the right thing to do in this matter? how much should i demand for the refund? thanks guys! hope you can help me with this.