hmmm... guess i was confused and the customer care e-certs really are discount codes unlike VDB vouchers which are funds and can go in my wallet. on the upside, though, the discount code reduces fare + taxes and is therefore worth slightly more than a voucher of the same nominal value you could deposit.

you could phone in and ask for help appying the e-cert to a companion reservation if you have no other way to use it, and ask them to waive the over-the-phone fee as you cannot apply both online, but they're so hamstrung in how they can apply electronic codes I doubt they'll be able to help. good luck. definitely use the companion fare for a roundtrip or longer itinerary rather than booking part of the trip with your customer care e-cert, unless it's an e-cert of really unusual size.