I booked an Audi A6, but when I went to pick it up, I was only offered a Touareg or a BMW 5-Series for an additional cost. There was also a random premium location fee.

I paid the full rental amount in advance, but the store charged me again without any notice. They provided no receipt and didn't inform me. This is very unprofessional. They promised to refund the extra charges to my credit card within 6-7 days, but they never did. Picking up the car was also troublesome. They said the pre-booked car was unavailable, and the provided car was too small for my luggage. It took about 15 minutes of communication to resolve this. However, I was satisfied with the car I eventually received.

Since I paid in full on the QEEQ platform, both picking up and returning the car were very convenient.

I was upsold full insurance multiple times during pickup, even after informing them I already bought it domestically. It was irritating and I couldn't drive at ease throughout the trip.
Otherwise, everything was great, convenient, and fast. I originally booked a manual wagon and paid an extra 10 euros to upgrade to an automatic Jaguar. It was a new car, and cars abroad get updated quite quickly.

Service varies from person to person, but overall, each experience has been good.