I have an iPhone 5s with iOS 7 on T-mobile in the US. I have a wifi network that is not connected to the Internet. When I connect to the wifi network with my phone, my iPhone tries to access the Internet using wifi only instead of using cellular data. Of course my phone cannot access the Internet using the wifi network because the network is not connected to the Internet. However it should be able to use cellular data.
How can I force my phone to use cellular data to access the Internet while connected to a wifi network?