My Samsung Eternity keeps asking for a code "Phone Lock"

Yes, your phone can use virgin sim card after unlocked. You will need samsung eternity unlock code to perform that process and you must remember don't put wrong samsung unlock code many times in your phone, it will make your phone in hard lock condition.

If it Network lock Code means ...You can Unlock the Mobile using the unlock code,You can get that at here
http://www.unlocking4u.com/samsung-eternity/rs6wp9/

you can unlock your phone here http://www.onlinegsmunlock.com/samsung-a867-eternity/rs7wp9/
They will provide the code when you enter your imei number,you just need to select your phone model and network provider

what exact lock does it asks?

phone lock, enter password? call 1 888 987 4357 for a free reflash

pin lock? ------------
pin blocked? /--------call the service provider because these are lock
puk locked? / on the sim not on the phone.
puk blocked?------

Most likely you have put a pin code on this phone. This code is stored in the SIM card and when you power up the phone it asks for a pin code before you can operate the phone.
In some cases when you enter the wrong pin code too many times the SIM card will lock up. You need to contact the phone service provider for assistance to unlock/remove the pin code.

sorry, there is no way to change that yet..... maybe someone will come up with a back door but i doubt it

What you have done is lock the sim card, not the phone.
Contact your provider and ask them for a PUK code. or you can go into your provider location and they will unlock the sim.
most providers have a default sim pin code like 1234 or 0000
so ask them what theirs is when you go in.
it lets you enter a wrong code 5 times and then locks it down for security reasons in case the phone is stolen

is it asking for a simlock code?
try 1234 or 0000

go to your settings options in the phone there will be a security option open it and there will be another option like phone and sim open it and u will se option like lock code , auto lock period all u have to do is to remove the lock code  or extend it time to whatever you want.if it ask for password and if u not know the password try 12345 or 0000 it will solve ur problem.thanks and take care of yourself