You will typically sign a mandate or power of attorney authorising your chosen commissionnaire to declare goods and interact with customs on your behalf; keep a copy, and understand that this authority is specific to the agent you signed it with, not transferable to a different company without your renewed consent. Hand over original documents (invoice, packing list, bill of lading, certificates) promptly, since a broker cannot file a complete declaration with a copy where an original is required, and a missing document is one of the most common reasons a shipment sits idle at port.
If a dispute arises, such as a disagreement over fees, a damaged shipment, or a mishandled declaration, raise it in writing immediately and refer to your signed mandate and fee agreement; a licensed broker operating under CEMAC accreditation is accountable to that professional framework, which gives you more formal recourse than an unlicensed operator ever would.