Europcar - Awful customer service and UNPROFESSIONAL

Europcar is bullying me to pay for hidden costs I did not know about when I was renting the vehicles. Their agents were charging the insurance rates which is apparently incorrect and now I'm held liable for the employees mistakes. I have sent many mails and not a single soul has been able to assist me and they don't understand it themselves. They had the nerve to hand over the matter to their debt collectors when they still have not resolved the matter. All they now is sending me unnecessary smses about monies are apparently owe but unable to answer my question.