Graph-API from VB.NET Script

In the Microsoft Site about using Graph API are example in C#.

https://learn.microsoft.com/en-us/graph/api/authentication-post-phonemethods?view=graph-rest-1.0&tabs=http

I try to do the following in VB.NET:

GraphServiceClient graphClient = new GraphServiceClient( authProvider );

var phoneAuthenticationMethod = new PhoneAuthenticationMethod
{
PhoneNumber = "+1 2065555555",
PhoneType = AuthenticationPhoneType.Office
};

await graphClient.Me.Authentication.PhoneMethods
.Request()
.AddAsync(phoneAuthenticationMethod);

Until now I have found how I can get the Authentication Token with: QER_GetAzureAccessTokenForApp

Is there any example on how we use this classes without doing REST?

In the moment we could not implement it with the GraphServiceClient, so we have a workaround with HttpWebRequest.

I can issue any HttpWebRequest in VB.NET and this works fine so far, but I want to use the GraphServiceClient instead of HTTP REST. 

Did somebody implement it that way already?

Regards, René