Please check whether the Customer has used up their Allowance. Regardless of whether they have Meeting Credits or a Meeting Package, if they have already used their allocated time, they will be charged the full price, according to their Client Type. 

Please read more about using Meeting Credits and Meeting Packages, as well as about How Meeting Room Booking Rates Are Being Applied.. 

You can check Meeting Credits or Packages on the customer's Account Record. If you need to check how much time a particular Meeting Package provides, you can do so by going to Settings > General > Customize > Calendar > Meeting Packages, where you can find the one you need and check its allowances.