When we requested a driver change, they said it was not possible and instead suggested adding a driver. They didn't inform us that adding a driver would incur a fee, nor did they have us sign any documents. Halfway through, we received a bank deduction SMS. Calling the store yielded no response, and even when we got to the store in Fussen, the staff couldn't reach the Frankfurt store via internal phone or email. Rent-A-Car tried to help us contact them throughout but to no avail. Finally, when we returned the car, we argued our case and they didn't charge us the fee. However, this made us anxious throughout the trip, affecting our travel experience.