Hi there!
The customer has local extension range numbers from (926 – 932) and PRA trunk series public numbers as (045269xxx –- 045269xxx) and local ext from 627 to 632 in an enterprise. Kindly find the below steps:
1. We created the number change index as follows:
a) we can also choose Trunk > Called Prefix Configuration > Advanced to access the Advanced Configuration page;
b) Click Number change index.
c) Click Create.
d) Configure the number change index to 1.
2. We created local call prefix as follows:
a) Configure the intra-office prefix.
b) Log in to the web management system.
c) Choose Trunk > CalleePrefix Configuration andclick Create.
d) Configure a prefix in the Create Prefix dialog box, 
e) OK. Prefix00 is configured.
Then we created call source and we will follow the below steps after we access theU1960 with putty software by sshconnection:
1. Add callsource 3:
a) Configadd callsource no 3
==== command executed success ! =====
b) Configure the trunk call source.
c) View GroupNo of SIP trunks.
show trunkgroup
d) Trunk information is shown in the command display area Trunk group information
2. Modify the trunk group information.
a) Modify the information about trunk group 2
config modify trunkgroup no 2 callsourceno 3
==== Command executed success ! ====
3. Configure the trunk bearer.
a) The calling number from U1960 is changed to 045269XXX.
configadd tgld callsourceno 3 officeno 0 protocol pra prefix 00 clipredeal yescliindex 1
==== Command executed success ! ====
4. Modify the information as follows:
Example
Modify the information about 1 user whose phone number is 926 and add them to call source 3.
config modify subscriber dn 926callsourceno 3
==== Command executed success ! ====
Or
Example
Modify the information 7 users whose phone numbers range from 926 to 932 and add them to call source 3.