Cheating car hire company with zero customer service!

Hi, I've used Woodford at least once before with excellent service. However my last experience with this car hire company has been disastrous. In summary, i hired a premium vehicle for one day on 29/09/18 and returned it on 30/09/18 to OR Tambo Airport, South Africa. I hired a BMW, they chose to upgrade me to a Merc Benz. When i took delivery of the vehicle they realised the petrol tank was only half full. they also noted that there was a dent/scratch on the front bumper. they agreed that i can bring the car back with a half tank petrol and that they were noting bot the dent on the bumper and the half tank petrol on their ipad gadjet, which i had to sign. Problem is that they have billed me for fuel and the dent on bumper and they don't return my calls, I've called three times and spoke to three different people none of whom return one's calls. Its just awful. Fist they give me an upgrade i did not want, then they give me half a tank of fuel and charge me for fuel i did not receive and lastly they charge me for a dent that was on the bumper. Terrible staff and i would not recommend Woodford!