Europecar

I rented a car from Europcar about six months ago.  A few days after returning the car I checked to make sure my deposit had been returned.  It hadn't - but they had taken more of my money out!  I was told it was because I rented the car on a weekend.  I was furious about this but they would not budge.  I asked where the hell my deposit was and they told me it would be returned to me and it was in my account the day  after.  Today when i went to pay for something using my card the transaction was refused - I was puzzled because I knew there should have been money in my account.  I got home and looked online at my banking details and saw that Europcar had taken £150 from my account. Not only did that leave me with an empty account, it also left me overdrawn and now I have to pay a charge to the bank - although they did say they'll refund it as a gesture of goodwill.  I have tried to contact Europcar through their agents and I've been told that there has been a 'computer error' and other people have been charged, too.  The woman i spoke to said someone will get n touch with me to sort it out and I've waited all afternoon but no-one has.  I'm bloody fuming here - why have they still got my details, even?  I know one thing - I'm going to get this sorted tomorrow even if I have to go down there and vault over the desk to get to someone!!!