There are several things that have to be considered when using sim cards out of different phones. Some of this info I have only realized in the last few days. I do intend to update my sim card info page.
 
I recommend that you do not ever turn a phone on with a sim card in it until you are certain that the activation process is going to complete successfully. When you turn a phone on with a sim card in it that sim card is locked to that phone and can never be used anywhere else. If during the activation process the system returns an error message and you can't activate that phone, you can't use that sim card again.
 
This information is addreessed toward retail packaged phones. Refurbished phones sold by Tracfone do not have the sim card numbers recorded in the system. The system will ask for a sim card number when activating a refurbished phone.
 
 
First you have to realize that these phones and sim cards exist in two differnt ways, a virtual state and a physical state.
The system knows that the phone and sim exists in a virtual state, it can not determine that they do not exist physically. It knows if the phone has had any communication with the system, that it did indeed exist in a physical state at one time. Just because a phone never communicates with the system does not rule out the fact that it can exist physically.
 
A phone is shipped with a sim card in it. The system knows exacty which sim card is shipped with each phone.
 
If a phone is activated and the system does not ask for the sim number during the activation process then the system "activates" the phone using the sim card number that was shipped with it. So, not only is the phone active in the system, so is the sim card that came in the package with it. Both the phone and sim now exist "virtually" in the system.
 
 
Let's look at the phone as the system sees it (virtually):
 
    The phone can also exist physically, but does not have to, these points are ony taken from the systems point of view so to say.
A phone was activated. Someone provided the serial number at activation so the system knows exactly which phone it was.
The phone can be put in an account and managed as if it exists physically. 
You can add airtime to the phone if you want to. 
You can just let it remain active until the service days expire.
    You can also transfer the service and number to another phone. You will need to provide certain information from the phone, as if it existed physically, in order to transfer service from it. 
 
 
    Let's look at the sim card from the systems virtual view:
 
A sim card was tied to the phone at the time of activation and a number was assigned to it. Remember this is positive virtually & possible physically.
The system used a sim card when the phone was activated based on one of two things. A sim card number we provided, or the sim card that was packaged with the phone. If during the activation process the system did not ask us for a sim card number then it used the sim card that was packaged with the phone. If it did ask us for a number then it used the sim card for the number we provided.
 
 
    Now just some general observations and information:
If you are going to use a sim card (physical) or a sim card number (virtual) other than the one that came packaged in the phone, make sure the system does ask for the number.
If the system does not ask for the number, it is using the virtual number for the card that came in the phone. So the system does not know which physical card you are using and the phone will not work.
Your only alternatives will be to make at least one, possibly numerous calls to Tracfone for at least one new sim; or to transfer the service from the virtual phone to another phone which will deactivate the phone with the wrong sim card in it. You will then need a new sim card to reactivate the phone.
 
Once a sim card number is used by the system it can't ever be used again other than  the possible reactivation of the original phone with the original phone number. This also has time restraints from deactivation to reactivation
If you enter a sim number that has been used, or is in use, the system will return a message that the sim card number is not in the system. Not in the system means it is not in the system available for use.
You can successfully use a sim card or sim card number in a phone other than the one it was packaged in.
If a sim card has been used then the phone that it was originally packaged with will have to have a new sim card in order to be activated. The system will see that the sim number that was package in the phone has already been used therefore it will ask for another number.