IPhones upgraded to OS 8.1 have been having issues with Wi-Fi dropping out, now I have to pay an extra 15 dollars because I didn't notice that the Wi-Fi signal I use at work disconnected. I don't think I should be responsible for the extra charges due to a fault with Apple's OS. FYI to fix the problem you have to go to Settings > General> Reset> Reset Network Settings. Then you can reconnect to your Wi-Fi network and enter your password.
Updating your phone to the new software is important Beta_T, we appreciate you doing so. I understand your concern with the overage charge, I'm sorry to learn there was a confusion when downloading the update on cellular data. I apologize, this is not an error on the manufacturer's end or the network. The reset is designed to delete all the network information from your phone, including your wi-fi savings and there is a disclosure about it. In addition, notifications regarding your data usage are sent to prevent overages.