Don't want to be with Straight Talk anymore? If you don't then this is the way to port your number to another carrier. If you go to a Verizon/AT&T/Tmobile/Sprint store and have a Straight Talk phone number you want to port, the carrier will ask for your account number and pin. So, what is the account number and pin? It's a very easy answer! Your serial number on the phone your using with Straight Talk is your account number. What about the PIN you ask? There isn't any PINS with Straight Talk.
So, next time you want to port over a Straight Talk phone number, just remember it's your serial number! (not ESN/IMEI)
Source: This information came from a ST representative and it worked!