PI to PI communication

Dear Experts,

We have a scenario from PI to PI .

R3 ---> Cust PI ---> Local PI ---> R3

We have to change the namepace, and message interface names. what are the changes to be made from our side to ensure that

the changes we make do not affect the soap header send to to cust PI. changes cannot be made in cust PI .

Thanks,

Aju