Set Outbound Caller ID as Customer Number

Hello Folks,
I am quite new to this forum. We have a small call center and our client has a new requirement for us.
We are required to transfer interested customers to a phone number given to us. This number has an IVR system, that confirms the customer’s phone number with them. Now this is the challenge. When we are transferring them to the clients phone it picks up our Caller ID and not the Customers Caller ID. We have set the 3-Way Call Outbound CallerID to CUSTOMER. But it still doesnt work. Our SIP confirmed the problem is at our end.

Here is our Dial Plan Entry:
exten => _81X.,1,AGI(agi://
exten => _81X.,2,Dial(${SIP9}/${EXTEN:2},tTor)
exten => _81X.,3,Hangup

Probably, If we can have a dialplan that pushes the Customer Number as Caller ID each time we shall be able to achieve this.

Please help me out I have limited knowledge.

DISTRO GoAutoDial CE 2.1
KERNEL 2.6.18-238.9.1.el5.goPAE (SMP)

I have changed my dialplan to this
exten => _9X.,1,AGI(agi://
exten => _9X.,2,SET(CALLERID(number)=${ViciDialCustomerPhoneVar})
exten => _9X.,3,Dial(SIP/${EXTEN:1}@net4india12,tTor)
exten => _9X.,4,Hangup()

Still nothing

0:42:38] – Executing [918555419851@default:1] AGI(“SIP/8015-00000014”, “agi://”) in new stack
[Oct 11 20:42:38] – AGI Script agi:// completed, returning 0
[Oct 11 20:42:38] – Executing [918555419851@default:2] Set(“SIP/8015-00000014”, “CALLERID(number)=”) in new stack
[Oct 11 20:42:38] – Executing [918555419851@default:3] Dial(“SIP/8015-00000014”, “SIP/18555419851@net4india12||tTor”) in new stack
[Oct 11 20:42:38] – Called 18555419851@net4india12