Re: Unlock without sim
Get your unlock code first from your phone's original carrier or buy it from 3rd party unlocker (each phone has its own unique unlock code). Then you dial ##7802# to bring out the UI to let you put in unlock code you obtained. If you already have an SIM card you want to use, you can skip the ##7820# because the phone will automatically prompt you to enter unlock code.
##7820# does not auto unlock your phone nor it send anything to your carrier to request an unlock code. You must follow the carrier's instructions to request unlock code (in most cases, if you are not their customer, you won't get one) separately.