Here's a step-by-step guide on how to disable or block iOS OTA updates on iPhone or iPad without jailbreak.
Here's how to disable automatic iOS 9.3.4 OTA update download from happening on your iOS 9.3.3 device. This is for jailbreak users only.
It looks like Google has started rolling out first OTA (Over-The-Air) update for Google Nexus S users. The update is officially marked as Android 2.3.1 Build GRH78 and it is just 1.9MB in size.