For a Xamarin application that sell a physical product, what is the best think to include in the application for the customer to contact my company:
I suggest all of them.
Besides budget/time constraints there is no reason not to give your potential customers the choice.
That way they can use the method best suited to their needs
If budget/time are an issue, I suggest you do the contact form and the phone link since they are "in-App" and immediate.
The email and SMS user experience is a bit more disjointed and can result in the customer not bothering.
Hope this helps,
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