Ok, easy enough, go to ld 20 and do a PRT of the TN's, then you can do a change;
REQ: chg
TYPE: 1120 <- Phone type of what you are changing
MARP NOT ACTIVATED
TN 96 0 1 23 <- The TN of what you want to change
ECHG yes
ITEM key 3 scr 7785 <- The key number then SCR for RINGING then the number
Then just hit enter a bunch of times.