Change and reset password

Hello everyone. 

I need to change the password of AD users from a web service. 

I have tried several options that I have found but there is none that works for me, 

I suspect that I must make the connection with AD with an administrator and from 

there to do the password change but I am not sure about it.  

The same case for resetting the expiration time of the password.  

Thank you very much in advance.