Problem:This is a rare scenario but being an Android enthusiast, I have faced it at least twice. So thought of sharing this small tip.
When you setup Samsung Tab for the first time. You need to select the wireless network and provide username and password to connect. While continuing with the setup wizard, in case you get a situation where you need to pause and resume later on a different wireless network, it is going to be impossible. There is no option to change the wireless network option/setting.
Going back using Previous button will not help beyond a certain screen. The only way is to restart the device using a long press on Power Button.