Hundreds of people from my company stayed at the M...

Hundreds of people from my company stayed at the MGM grand for our annual conference.
They charged many of us fees that should not have been charged,($500 USD) although everything was paid for in advance by our company. The funny thing was, when I told them I won't be paying the money and mentioned my company name, the guy cancelled it straight away, but for the rest of my team, they went ahead to charge them.
This is extremely dodgy. Do not want to give them our company's business again.