how to set proxy for connect to vuforia cloud in my app(export android and ios)

Hello everyone
I'm developing an app that users can connect to the vuforia web service(Vuforia cloud) and recognize targets in their cloud servers. for some reasons I want to set a proxy server that all users use it to connect Vuforia cloud. I mean that they must connect to internet with proxy. and I want to build(export) both android and ios version. how could I set a proxy setting for connecting internet in devices.(I want to write a script to do that automatically for app internet setting, I don't want to set proxy for end user devices manually).
I've been searching all the forums and didn't find a solution that works. and I'm new to unity and vuforia so maybe there is a solution that I didn't figured out.
in scripts I find GlobalProxySelection that I think works for set proxy for all web requests. but it is deprecated. and it says use webrequest.defaultwebproxy instead. but I don't figured out how to use it to config proxy for global use of internet.
I am really sorry for my bad English. please Help me in this.