Charged for windreen replacement due to pre-existing chip that became a crack

Hired a car recently. We went through all the dents, cratches and chips before driving off. There were several chips on the windscreen. We had taken a super cover with the understanding it covers everything. No one spoke of glass and tryre cover as an extra cover necessary. We drove from Durban to the Eastern Cape and it was very cold there in EC . We got back to Durban the following day and found the area warm. While driving back to Shaka Airport to return the car, one of the chips on the windscreen expanded to a 10 cent coin size crack from, presumably, change in temperature as there were no vehicles around to dislodge loose stones. This was explained to the gentleman receiving the car. Story short, the windscreen was replaced and my credit card was charged with R3, 050. Stay away from Woodford King Shaka Airport, period, and take supercover and glass and tyre cover from other car hires to avoid headaches. It's up to you though, maybe you want my experience first before you learn.