My age-old UA/CO mixed-pnr issue still exists.

Flight #1 on UA
Flight #2 on CO

Both show up on my co.com reservation. Apparently I get OP miles for the UA segment.

But, the issue that I have now, because the UA segment is there, I can't go change the CO segment and if I try to do it over the phone, they'll want to charge me since it was booked via the corp agent.