Personally I would call the DM or PM line yet again and talk to a supervisor or whatever to straighten it out before going to the airport. Don't hang up until your boarding pass prints, although you'll probably still have to show your passport to a DL agent at the airport. I've been able to do OLCI with SWUs, although DL's earlier pre-merger paper version seemed to require reticketing at the airport. For a while this caused confusion--they kept telling me I needed to turn in the paper certs at the airport and after arguing I would bring printout from my computer with me--but DL seems to be doing better on this during the last several months.