Update User-Name AVP on Post Auth module

Hello Everyone, I am aware that It's not good to alter the User-Name but I have a requirement. I am authenticating an EAP_TTLS request and during the Post-Auth section every module in the Unlang is being called by *modcall_recurse*, one such is the policy module where I update the User-Name along with other standard AVP in reply just to verify. As soon as the control came back to the modcall.c *User-Name* value alone kept intact. Is there some sort of callback or method handle that reverts back the User-Name to its original. Thanks, Suriya