We rented a car from SixT on our trip to Iceland. Initially, the agent that assisted us upon arrival was very nice in person and told us that we would not have to worry about our mileage limit since we would be able to call to switch to unlimited mileage at any time if needed. When we decided to switch during our trip, we called and emailed the business many times, but never received a straightforward answer. The information desk would tell us to send an email first, to which we responded that we had sent multiple, before they would apologize that they were busy and hang up. We tried to contact them numerous times on multiple days and different times of day, but the response was always the same. Additionally, there was no information on the website at all. We started to skip many of our planned attractions in order to avoid going over the limit too much. SixT never reached back to us. When it came time to return the car, another agent told us that we would have to pay an additional fee. Not only were we misled by different employees, but we were also treated with a very rude attitude. As we were discussing, the manager Mr. Grzegorz (from the Reykjavik Keflavik Airport location) ignored us and even told us to move aside so he could tend to another customer while we needed to catch our return flight. We asked if we could talk to a supervisor in order to voice our concerns and resolve the situation, but we were still ignored. The entire interaction was unprofessional. All of this inconvenience was caused by the lack of communication on the company's side. We had chosen this company because it is one of the largest companies in Europe, but this has been by far the worst customer experience I have ever had.