It is a condition for invoking the guarantee that the end user within the Warranty Period submits a written complaint no later than 14 days after the end user found or should have found the defect. The complaint must be sent to Caball Therapy Systems (CTS) or to the authorized Caball Therapy Systems reseller who has sold the product. The complaint must be accompanied by documentation in the form of an invoice or the like. which proves that the product was purchased either by Caball Therapy Systems or by an authorized Caball Therapy Systems reseller.