Here are the code for soft reset *#7380# and hard reset *#7370# nokia mobile. Hard reset delete data on your nokia e5 but it will also remove your security code and reset to default. this will unlock your nokia mobile. and it your mobile is sim locked than t-mobile unlock and at&t mobile sim unlock is different.
How to Network Unlock Att Mobile
. in that case you need sim unlock code for your nokia. you can get free from online as per your imei number. even you can do bootloader unlock on your nokia mobile.
here is other way to unlock nokia mobile.
First power off nokia mobile then simalteneously press and hold power button, *,3and call button. Once nokia log on screen release all key button. This will factory reset nokia. Default nokia code is 12345.