Thank you for your reply Kostas.
To unlock your phone please follow the steps below:To perform factory/hard reset please follow those steps:1.
Turn the power off. Remove and replace battery.2. Press and Hold
the Volume Up, Home and Power button.3.
When the start up screen show, release all the buttons.4.
Use the Volume Up/Down button to navigate to "wipe data/factory reset"5.
Select "wipe data/factory reset"6.
Select "Yes -- delete all user data"
* Allow several minutes for the factory data reset process to complete.7.
Select "reboot system now"
* Allow several minutes for the reboot process to complete.
Please note that this procedure require some practice. If you prefer video instruction please check the video below - click here
Please don't hesitate to ask if you have any difficulties. I will be happy to help with any follow up questions.If you have any difficulties or you need more information please do not rate my answer negative BAD service or POOR service. Reply to me using "Reply to Expert" button and I'll provide you with more help.