Plan A/Plan B makes it so that you can have parallel billing plans, where the same service incurs a different charge, depending on whether the patient is part of billing plan A or B. Typically, Plan B is the standard (default) charge, while Plan A is the discounted rate if a discount applies to the specific service. However, this terminology is configurable.
The charges for Plan A and Plan B are set by you in your practice's charge list. If you do not need or want a two-tier charge structure, you can simply ignore Plan A and use Plan B exclusively. By default, patients coming into the system are placed in Plan B.
To change the patient's billing plan, click on the edit icon in the upper right-hand corner of the Patient Information block and then on the Billing Info tab. Then toggle the radio button between Plan A and Plan B, and click "+ Edit Patient" to save.