preproxy_users doesn't filter attributes

[Michael da Silva Pereira]

Hi All,

I am wondering if anybody has done this, I'm sure it's actually very 
easy to do, But I'm just not able to get it done :(

I need to filter requests coming from my NAS going to my radius server 
being forwarded to a clients radius server.
Now I am able to modify and update attributes, even add using 
preproxy_users. but how on earth do I drop the attribute completely?

Currently in preproxy_users:
DEFAULT Realm == "testrealm.com"
    NAS-IP-Address := 196.3.121.32,
    User-Name =* ANY,
    User-Password =* ANY

Other server still recieves:
3GPP2-Correlation-Id
Calling-Station-Id
Framed-Protocol
User-Name
User-Password
Service-Type
NAS-IP-Address
NAS-Identifier
Proxy-State
User-Password
Client-IP-Address

Kind regards,
Michael da silva Pereira