New Zealand South Island Self-Drive - Christchurch Airport to Queenstown and back

I rented a car for 12 days. On the 14th day, I found a thumb-sized bubble on the tire and wanted to know how to properly resolve it. The car rental store did not answer the phone, and the company’s customer service was unresponsive after several attempts. I had no choice but to drive to the Queenstown airport store for a solution. The service staff quickly handled the car exchange without mentioning any cost. However, when I returned the car at Christchurch Airport on April 29, the company charged my credit card without explanation. When I asked the store for an explanation, they said it was for the tire replacement fee and gave me a phone number and email to contact the company. This way of handling the situation is unacceptable. Issues: 1. The cost was not mentioned when exchanging the car. 2. The responsibility and cost for the tire issue were not explained but directly charged without prior notice. Better service is needed, especially in providing Chinese language support to avoid communication barriers.