Do not contact client after they say they will

My company booked a 4x4 for me to fetch at Europcar. When I got there, I received the wrong vehicle. Europcar fixed the issue. A day or 2 after I returned the vehicle, I got an email (to my personal email address) from Europcar whereby they sent me an invoice for the wrong vehicle. Saying I owe them money. Firstly, I did not make the reservation so I don't appreciate getting the invoice - especially to my personal address. That is my companies issue - not mine. Secondly, when I phoned them to correct the issue, they said they'd call me back. 2 days later I had still not heard anything. I phoned again and spoke to someone else. They said they'd call me back. I waited another whole day and still heard nothing. Eventually I had to phone back again another day later before the issue was resolved. I do not appreciate being told that I'll get called back, only to not hear anything. That is not how one does business. Especially if it's with a client who is paying a lot of money for a service that should run smoothly. They could see I was annoyed, yet I didn't even get a slight hint of an apology. Europcar needs to pull up their socks & start treating issues with professionalism & urgency.