If a Virtual Mobile Number (VMN) for a certain country is not available in 'Buy a number' menu, this means that either we do not offer numbers for this country or purchasing a number is linked to certain requirements. In this case, please do reach out to firstname.lastname@example.org for assistance.
To buy a number in certain countries, it is often a requirement to provide a registration number. When you register a business in your home country, you always get a registration number. For the US, you can find more information here.