Translate IP SIP Owner/Creator and Connection Address in Message Body

Dear DC,

I have an issue related to SIP Trunk that goes through F5 Big-IP, which the SIP trunk traffic was requested from our PBX Server to the SIP Trunk Service Provider. And it's not working when the client makes a call through the SIP trunk to the mobile phone. I have configured a VS for this traffic, and I see the traffic was translated as my expected. But when we do a capture at SIP Trunk Service Provider site, we still see the private IP of my PBX server sent the INVITE Message. 

So, anyone knows or has experience how can we translate the IP address in the SIP Message Body? I appreciate your response.

Thanks and Best Regards,

Phaneath