Best way to do this is with Pretranslation.
These are the instructions from GHTROUT (RIP).
You may want to check to see if it is already enabled on your switch by printing the FTR_DATA in LD 21.
Dial Out Without "9"
Making it so you don't have to dial 9 on a set - by using the pretranslation feature. Note dialing internal is a challenge when you set a phone up this way - but there are applications when it is needed. Note: for this "example", speed lists 90, 91 and 92 were created - do NOT use existing lists - make new lists.
-----------------------------------------------------------
Build three NEW 10 member speed call lists. Two are empty and the third is populated as shown in example SCNO 0092. Note my list numbers are EXAMPLE NUMBERS only.
LD18
SCNO 0090 (or the list number you created)
SCL
DNSZ 4
STOR 0
STOR 1
STOR 2
STOR 3
STOR 4
STOR 5
STOR 6
STOR 7
STOR 8
STOR 9
SCNO 0091 (or the list number you created)
SCL
DNSZ 4
STOR 0
STOR 1
STOR 2
STOR 3
STOR 4
STOR 5
STOR 6
STOR 7
STOR 8
STOR 9
SCNO 0092 (or the list number you created)
SCL
DNSZ 4
STOR 0 90
STOR 1 91
STOR 2 92
STOR 3 93
STOR 4 94
STOR 5 95
STOR 6 96
STOR 7 97
STOR 8 98
STOR 9 99
-----------------------------------------------------------
BUILD THE LINK BETWEEN PRETRANSLATION AND XLST:
LD18
SCL000
REQ NEW
TYPE PRE
CUST 0
XLAT 0 PRE 90 (or the list number you created)
XLAT 1 PRE 91 (or the list number you created)
XLAT 2 PRE 92 (or the list number you created)
XLAT
-----------------------------------------------------------
ACTIVATE PREO IN CUSTOMER DATA
LD15
REQ: CHG
TYPE: FTR
TYPE FTR_DATA
CUST 0
OPT
DGRP
IRNG
PKND
SPRE
PREO 1
-----------------------------------------------------------
CHANGE THE PHONE
LD10 OR LD11
REQ: CHG
TYPE: [TYPE HERE]
TN [TN HERE]
ECHG YES
ITEM XLST 2
ITEM
-----------------------------------------------------------
Now you can dial a number without "9". However, you cannot dial internal extensions, since a "9" will be inserted in front of everything you dial.