Ways to protect phone from hacking through a wifi network when travelling

This problem is solved by using a VPN. Using a VPN, your data is not visible in plain-text to someone who is capturing the network traffic.

Depending on how "techie" you are, you have various options.

• If you are not technology savvy, look for a VPN service. There are a lot out there, but product recommendation is out of the scope of stackexchange. Just be aware to not use any free provider.
• If you are proficient with computers, you can create your own VPN server using a cloud provider (AWS for instance). A common software used in this case is OpenVPN. A good thing of AWS is that there is available a preconfigured virtual machine (AMI). Here you have a tutorial to set everything up.