The most common reason why a client gets billed with the wrong waiver is because the waiver is setup incorrectly in a Span Date on the Client Information screen.
Basic Information
Span Dates
In this example, the Waiver is setup for Level 1 in the Basic Information section. But because of the Span Date setup, any billing done in 2017 would be using the I/O Waiver. It doesn't matter how the Waiver is setup in the 'Basic Information' section, the Waiver as defined in the Span Dates will take precedence.