Hi I am not able to do SRTP configuration properly

this the kamailio configuration 

route[NATMANAGE] {

rtpengine_manage("replace-origin replace-session-connection RTP/SAVP");
}

I can see in SDP RTP/SAVP but still the packets are RTP.

clients used linphone-android (media-encryption is SRTP ) and 3cx-windows-client

You have to differentiate between offers and answers. In the offer going from RTP to the SRTP client, instruct rtpengine to use RTP/SAVP. In the answer, omit that option (or use RTP/AVP). Indiscriminately calling rtpengine_manage with the same options in both directions doesn't work.

Cheers