Note that a CDRs provider is not a Vendor, also if in many configurations there is a one to one to one match between a Vendor and a CDR provider. There can be configurations where the same CDR provider is used from many Vendors (you retrieve CDRs from ony of your VoIP server, configured for collaborating with many VoIP providers), or a Vendor can use more than one CDR provider (the Vendor uses multiple FTP accounts).