I do have a problem, car dealership refund .?

Last Friday I went to a used car dealership, we inspected a car and we asked if the car leaks oil , they said no we asked if the car has any problem they said no. we tested the car and we were like lets buy it, but we didn't have the whole money, so we gave them, 2500, we told them we wanted the whole front window changed because had minor crack, the car clean, they said okay, so next day on Saturday , we arrived to pick up the car and nothing was done, plus my mom was kind of worry about oil leaks so she gave us this white paper and said to me i want u to touch the whole bottom of the car and see if it really doesn't have leaks, so after i do it i found oil drops in it, so the car salesman say i cannot help u this is your car already,so then my dad was if u fix that problem we buy the car and the guy said okay we will do it on Monday, so when we got home , my mom got very upset because she doesn't want a car that leaks oil,so we call the guy and we said we don't want the car and he said oh we already fix everything ( after half hour ) come we can talk about it. my talk to the guy and said u lied to me to me i asked if the car is leaking oil u said no , and so we want our money back the guy said we can talk about it. but my dad has not sign anything no contract , no nothing , the only thing he did was gave them the money as a down payment. we got a receipt that does't not say anything about not being refundable or not. we do not know how to proceed. help thanks