Accounts department is an absolute shambles

I'm really getting fed up with accounts department who are showing a very nonchalant attitude with regards to addressing an incorrect invoice where I've been grossly overcharged. To mark off a query as answered and yet the response does not even explain what's happening in that invoice is an absolute show of laziness and unwillingness for people to do their job. I'm sick and tired of calling and reporting the same issue now and my next call will be to cancel because this is really looking like a Mickey Mouse operation now