Bypassing VPN restriction in another app I want to know if its possible to trick this app &quot;Diitalk&quot; into either thinking I am in US or blocking it from knowing that my VPN is working cuz if I dont have a US based IP, it wont let me use the US based number.

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Can this be done on the android device itself without having to use a VPN router or any other device?

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VPN detection is usually done on server side. 

Diitalk simply has to check your IP and compare it to a list of IP ranges by common VPN providers. If the IP is in the IP range of a known VPN provider it blocks you. This is known as blacklisting.

Therefore the highest change to bypass such a VPN check is to use a custom server and install your own VPN on it. If the server's IP is not in a range used frequently for VPN your VPN may stay undetected. 

However the service you are trying to use may use a different VPN detection technique, like whitelisting. The IP ranges from US telecomunication providers are known and one can simply check if the IP is within a range or not. In such a case any VPN provider or self-installed VPN will fail.