If a supplier has not fulfilled its commitments to a service he owes you, he should be informed so that it can honour these commitments.
If it is a claim on an order, you must open a claim - Process Open a claim
You can contact the supplier directly either by phone or by email by finding his contact details in your platform - Supplier's page.
You can also contact your Customer Service who will take over if you need it.
You can contact your Customer Service by email at firstname.lastname@example.org and an advisor will answer you within 24 hours.