You do not magically get unlimited internet out of air. You will do need a separate mobile internet contract from AT&T, T-Mobile or other mobile carriers to use with the Ryoko Wifi. The Ryoko Wifi does not do anything that cannot be done via your mobile phone's hotspot. A sim carrier that requires monthly top-ups or a contract is still required to access wifi which can be obtained via a cheap mobile phone at a fraction of the price!
Muama Ryoko Wifi's Website

Instead of buying a Ryoko Wifi, you can turn on Mobile Hotspot or Tethering on your cellphone or mobile phone to connect your devices to the internet. There is no need to buy this product that is misleading consumers with claims of unlimited internet, no surprise roaming fees while traveling, and 150 mbps superfast and secure 4G LTE internet connection. Remember, your internet speed will depend on your mobile carrier and the plan you have purchased from them.