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It seems you didn't pay UA, so ipso facto they can't refund you.
The rest is a bit of a mess. You can try writing to UA and complain that due to the way your ticket was handled during the re-accommodation you were charged baggage fees and you feel you shouldn't have been, and depending upon their view of what ticket and upgrade you bought, they may issue a credit to make up for it.
As a side note, 120USD seems quite cheap for a Premium Economy upgrade. Do you have an record of what was offered, especially re: bags?