Is there a way to set my phone to use internet only on Wi-Fi?

In your phone settings, there will be an option to turn off Data, do so, then turn on the wifi and connect to your local wifi spot. You'll still receive calls/texts but as long as you're connected to wifi, you'll also be able to use the internet. I don't know how the internet goes through an SD card, but that's pretty interesting if it does, please, tell us how that technology works! :) Good Luck

its not an SD card. its called a SIM card. turn off ur data connection in settings and use wifi! that should sort ur problem.

hope this helps :)