Oil Tank not closed messedup my Car

Good Day I went to Bp Norwood Mthatha to fill up petrol I asked the petrol attendant to check the oil. And he said I must refill oil, when I left before I reached my destination I noticed a funny smell while I was driving. I went to look there was oil everywhere the oil cap was not closed. I went to the shops to buy oil so that I can take there car back to Bp. They washed the oil with engine cleaner. And refilled the oil. But now the car is giving me problems so the manager at bp is nowhere to be found , when you request to speak to the manager the petrol attendants lie and say he is not around