Have you tried creating a responsive site to load in the WebView?
Another option is to load it in SafariController.
Edit: Please also note that if you sell digital goods you will have to do it through InApp Purchases as only for physical goods Apple allows an outside charging institution.
@ Semen, thank you, but I cannot add a header in the webpage markup as it is not my webpage, it is a payment gateway's website that I am showing in the webview.
@ Hatzisn, also thanks, but same problem it is not my website so I cannot modify it.
Dim javaScript As String = $"
var meta = document.createElement ('meta');
meta.setAttribute ('name', 'viewport');
meta.setAttribute('content', 'width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, user-scalable=yes');
document.getElementsByTagName ('head') [0].appendChild (meta);
"$
WebView1.EvaluateJavaScript (javaScript)
I am not sure that a problem is relative to zoom scale. Probably incorrect webpage design. But you can play with initial-scale (shold be between minimum amd maximum scale)