Switch Xbox account assocation (gamertag B to account A)

There is no way to completely delete an Xbox account from the servers. You can delete the Microsoft account, but the gamertag will still be on the servers. So the only way would be to pay for two changes. I don't have a link I can give you as far as a source.
That's just how it's always been. Multiple people have asked the same thing over the years.

You would have to first change the gamertag of the one you're wanting to use to something else in order to free it up for use on the account you want to use it on. Then you'd need to change your current gamertag to the one you're wanting to use. You will
have to pay both times.

Source, please? I am aware that this is one way to handle it, but I would rather delete the account than pay for two changes.

You would have to first change the gamertag of the one you're wanting to use to something else in order to free it up for use on the account you want to use it on. Then you'd need to change your current gamertag to the one you're wanting to use. You will
have to pay both times.

Hello CUZINCUZ613

Switch gamertags between two Microsoft accounts

If you try to switch your Xbox LIVE gamertag to a Microsoft account that is already linked to another gamertag, you will receive a message that says “the Microsoft account (or Windows Live ID) you’re switching to is already linked to another Xbox account.”

Before you can switch your gamertag in this case, you must first remove the existing gamertag from that Microsoft account:

1. Create a new Microsoft account. You will only need this new account as a temporary means of moving your gamertags. After the gamertags have been switched, you will no longer need this Microsoft account.
   
   Example:
   
   Gamertag A is linked to Microsoft account 1.
   
   Gamertag B is linked to Microsoft account 2.
   
   To swap gamertags A and B between Microsoft accounts 1 and 2, first create a third temporary account: Microsoft account 3.
   
2. Switch the gamertag that is linked to the Microsoft account you want to use to the new temporary account you just created.
   
   Example:
   
   Gamertag A remains linked to Microsoft account 1.
   
   Switch gamertag B to Microsoft account 3.
   
   Microsoft account 2 is now free.
   
3. Now switch your gamertag to the Microsoft account you want to use.
   
   Example:
   
   Switch gamertag A to Microsoft account 2.
   
   Gamertag B remains linked to Microsoft account 3.
   
   Microsoft account 1 is now free.
   
4. To complete the swap of gamertags between the two original Microsoft accounts, you must wait 30 days. (A gamertag can be switched only once every 30 days.)
   
   Example:
   
   Gamertag A remains linked to Microsoft account 2.
   
   After 30 days, switch gamertag B to Microsoft account 1.
   
   Microsoft account 3 is now free and no longer needed.
   

Hello PAPABEARSMOKEY

Switch gamertags between two Microsoft accounts

If you try to switch your Xbox LIVE gamertag to a Microsoft account that is already linked to another gamertag, you will receive a message that says “the Microsoft account (or Windows Live ID) you’re switching to is already linked to another Xbox account.”

Before you can switch your gamertag in this case, you must first remove the existing gamertag from that Microsoft account:

1. Create a new Microsoft account. You will only need this new account as a temporary means of moving your gamertags. After the gamertags have been switched, you will no longer need this Microsoft account.
   
   Example:
   
   Gamertag A is linked to Microsoft account 1.
   
   Gamertag B is linked to Microsoft account 2.
   
   To swap gamertags A and B between Microsoft accounts 1 and 2, first create a third temporary account: Microsoft account 3.
   
2. Switch the gamertag that is linked to the Microsoft account you want to use to the new temporary account you just created.
   
   Example:
   
   Gamertag A remains linked to Microsoft account 1.
   
   Switch gamertag B to Microsoft account 3.
   
   Microsoft account 2 is now free.
   
3. Now switch your gamertag to the Microsoft account you want to use.
   
   Example:
   
   Switch gamertag A to Microsoft account 2.
   
   Gamertag B remains linked to Microsoft account 3.
   
   Microsoft account 1 is now free.
   
4. To complete the swap of gamertags between the two original Microsoft accounts, you must wait 30 days. (A gamertag can be switched only once every 30 days.)
   
   Example:
   
   Gamertag A remains linked to Microsoft account 2.
   
   After 30 days, switch gamertag B to Microsoft account 1.
   
   Microsoft account 3 is now free and no longer needed.