Bad service and product damage

I had an encounter where I poured Petrol instead of Diesel at Shell soweto convinience Garage at mofolo Crossroad.My car was towed to a workshop in Midrand ofcourse to the Shell Garage Designated workshop at their expense ofcourse.I had poured 1k Petrol because I was on my way to Limpopo to work on clients and ofcourse I couldnt make it to Polokwane for that particular client to work on which caused me my work ethic and Money because I couldn't continue with the trip.I would like to attest that I spent the whole month of August to almost end of September just for my car to be fixed,during the waiting I had to beg for feedback and lose on business and also had to Keep my daughter home because I drop her at school and at that time I couldn't because I had no car.I would like to attest that these people took a whole month and couple of days to drain my car and return it wherelse they said they will change parts,to my surprise I asked them to mitigate my August and September expenses(Fees,food and policies) just so I don't default because I use my car as form of transport to go work on my clients which they refused and said they can't because they spending thousands on my car which is almost 38k as I quote,now on the day I went to fetch the car I asked for the invoice,only to see that they only spent 2,8k on fixing the car and I was cost a whole 20k of two months by their inconvinience which they refused to mitigate,now my policies and daughters fees are two months behind and I can't carry that backlog but because they had said they spent 38k on my car ,I am actually keen on reporting this matter to Shell SA so this matter can be investigated and I have August and September expenses covered by shell because I will not accept deciept from them when business continued as usual and they never apologized formally and now my car is making funny sounds and smell and qhen I talk to them they are not interested.I would like to note that after draining the Diesel,qhen they returned my car they didn't want to return the 1k FUEL I paid for and I had to beg and grovel.After receiving the invoice today which is a month later,I am honestly seeking mitigation in this matter.