Echo back problem

Analog PSTN telephone line is connected to asterisk server which receive calls and play some IVRs. As response to the IVR we have to dial some numbers and record our voice. During dialing number, it echo back dial tone. For instance, if we dial 5 it plays tone corresponding to 5 and after some delay it also plays same tone again(echo of that tone). However, there is no problem when i call using sip softphone.

I had already tried

echocancel = yes
echocancelwhenbridged = yes

and auto generated system.conf look likes

# Span 1: WCTDM/4 "Wildcard TDM400P REV E/F Board 5" (MASTER) 
# channel 3, WCTDM/4/2, no module.
# channel 4, WCTDM/4/3, no module.

# Global data

loadzone= us
defaultzone= us

loadzone is US although i am here from Nepal (Land of Highest mountain “Mt. Everest”)

Is there any way to solve this problem ?

Are you actually talking about duplicated digits, rather than your echoing the remote dialtone back to them? Dialtone is the tone that prompts for the digits, not the digits. If so, echo cancelling is irrelevant, as this isn’t an echo problem.