enh: add billing info header to avoid confusion

[uds5501]

Fixes #3291

Short description of what this resolves:

Adds a billing information header to indicate what are the extra fields for.

Checklist

• I have read the Contribution & Best practices Guide.
• My branch is up-to-date with the Upstream development branch.
• The acceptance, integration, unit tests and linter pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)