this email is not available. choose a different address

1. Sorry for bad English.

2. I have 2 apple IDs.

3. Apple ID "A" linked with email "A" and Apple ID "B" linked with email "B"

4. I changed email "A" to "C" on Apple ID "A", now email "A" was free.

6. I wanna link email "A" to Apple ID "B"

7. but i got this error "this email is not available. choose a different address"

8. what i can do, please help me !

Message was edited by: surasit.laopa