Pentravel - Nambia - Refund Dispute

I booked a holiday package for May 2018, to Namibia. The booking was inclusive of a 4x4 vehicle due to the harsh terrain. However, upon arrival at the Windhoek Airport I was issued with a non 4x4 vehicle and subsequently complained to the consultant, which they could not assist. Subsequently, I notified Pentravel of this mistake upon arrival at the Sossusvlei lodge and requested a swop out. I had to then travel all the way back to Windhoek Airport to have it exchanged. I received the Toyota Fortuner 4x4 and departed to my next destination within Namibia. When I returned to South Africa a SMS message noted that I did not receive a full refund by Europcar, which amounted to approximately R4500.00. After a number of enquries I was told that this was due to the "upgrade" to the 4x4 model. I then lodged a complaint as my contract with Pentravel included the 4x4 model. Subsequently, they changed the reason to the fact that the non 4x4 vehicle's window cracked. I then reported to them that I had a super waiver and could not be held responsible for this. The operator contracted by Pentravel rep**** that I must provide proof of any waivers. I contracted with Pentravel and not their subcontractors. It has been months now and I have not had any refund or reimbur*****t.