Follow this. http://www.tp-link.com/en/article/?faqid=227

Hi Frank, can you access internet if clients connected to LAN ports of Archer C7? Try to modify some wireless setttings, like channel.

What's the WAN IP address for WAN1 and WAN2? They shoud be public IP addresses.

http://www.tp-link.com/en/article/?faqid=572

Are you able to connect some other wireless clients to the Wi-Fi Hotspot created by iPhone 5S? Is it stable enough? Did you try to follow this instruction? http://www.tp-link.com/en/article/?faqid=679

When connection drops, try to login http://192.168.0.254 and check if there is WAN IP address. Try to change a channel on Wireless---Wireless Settings page.