Firstly, unlock your device by entering null as password together with your Google username without @gmail.com. If it doesn't work, contact your mobile service provider and ask them to activate the Data Connection. Once you have access to Internet you will be able to use your Google account to unlock the device. Alternatively, you can install Screen Lock Bypass Pro from Google Play Store. It will allow you to bypass the lock screen and reset/remove your screen lock password, pattern or PIN. If none of these help, you will need to perform a factory reset. Turn off the device and then press Power + Volume Down for 10 seconds until you activate the Recovery Menu. Select Wipe Data using the volume buttons and Power for the OK button.
