petrol cap not put back

On Friday night I went to put petrol at Bp in Kew .The next day I realised that they did not put back the petrol cap. I went back to notify them about it, they said they would look into the camera to see footage and they then realised that they actually didnt put it back I was then asked to come back the next day.Tshepo(manager) then asked that I fetch it on Wednesday and I did and was told that Tshepo was not in and was then asked to buy it and will be refunded but they have not yet helped me out.