Pathetic service and failure to uphold agreement

I went to our local filling station during February (19th) to have diesel put into my diesel vehicle.<br> However after confirming diesel and it stating diesel by the filling cap the attendant put petrol in my vehicle.<br> I was inside the store to pay and when I came out to my car the attendant had already informed the Manager who was standing at my vehicle and had instructed the attendant to top up the tank with diesel in order to flush out the petrol.<br> She told me (Manager, Annalene) that this is what was happening and that it would be safe for me to drive my vehicle to Stellenbosch (30km away) and that it would be fine. I then asked for her details as if there was anything that were to happen to the vehicle on the journey I would contact them as this was their advice / confirmation. She agreed. I then called Annalene to advise that I had arrived and that I was advised I should not have drive the distance. She informed Owner and agreement was they would cover the bill of having vehicle drained / cleaned out and put in diesel. <br> My husband went there today after sending them the invoice and the Owner said he will not do anything.<br> This is a breach of what was agreed, small claims court!