i just bought the same mifi device from low yat the other day (cheap price and didnt hesitate to negotiate the price) and got the same problem with my iphone..however, i found the solution (after tedious 3 days playing with the settings and configurations!!!) this will work for connecting apple products (macbooks, iphones, ipads, etc) to the device...i even got the router to be password protected as i am using the WPA Wireless Security - which im having trouble when i start using the device.

1. go to ur web browser and enter 192.168.0.1 to log in to the router admin.
2. go the the LAN SETUP tab and and find the DHCP RESERVATION.
3. enter ur device name for identification (and no spaces allowed) and enter the ip address according to the router ip address.
4. as for the MAC ADDRESS, u can find it at ur iphone at SETTINGS>GENERAL>ABOUT>WI-FI ADDRESS and enter it in the field as per ur device. for macs, u can find it in the network preferences - if u can connect to the internet on a mac, i'm sure u can find the AirPort ID.
5. save the setting and re-connect to ur mifi and hopefuli everything will go right this time - it did for me..

all the best guys!!!