This article covers turning off MAC randomization on Android devices.
Step 1: Navigate to your phone's Wi-Fi Settings, then touch the gear next to the network.
Step 2: In the "Network Details" screen that comes up, press "Advanced"
Step 3: You should now see a "Privacy" setting with the subtitle "use randomized MAC (default)" press this and select "Use device MAC" on the menu that pops up.
That's all!