O,tested test,12345
OC,test explore,34567

O,new order
OC,new quote

New order,tested test,12345
New quote,test explore,34567

join -t, -j1 -o 2.2,1.2,1.3 <(sort file1) <(sort file2)

$ awk -F, -v OFS="," 'FNR==NR {a[$1]=$2; next} {$1=a[$1]}1' f2 f1
new order,tested test,12345
new quote,test explore,34567