Where are you flying in from for your vacation? I often travel around Europe and always use servises GetTransfer. They have professional, polite drivers who know the area well. You can read reviews on their website https://gettransfer.com/en/directions/montenegro and book a car for your desired date and time. A friend once told me that he went hiking in the mountains and thought the driver was lost because there were no other cars on the road and the GPS showed a different route. However, the driver knew the way and took him to his destination.