Magic Jack would not accept pre-paid VISA gift card number for payment for registration. I do not use my credit or debit cards for purchases online for security reasons. That is what pre-paid VISA cards are for.
Magic Jack will accept a type of Paypal payment, but I understand that Paypal also requires that you link a credit or debit card to your Paypal account – you can't just deposit money with them & use only that amount.
As far as I'm concerned, anybody online that insists on having access to my regular credit or debit card is a potential scammer and I can't afford to be robbed. I'm taking MagicJack back to the store where I bought it.