I have 2 phones in 1 account,

phone 1: 123

phone 2: 321

how can I make sure either of these accounts: 

Account 1:

phone 1: 321

phone 2: 123

Account 2:

phone 1: 123

phone 2: 

Account 3:

phone 1: 321

phone 2: 

can't be saved to the system?

meaning when you create it, input the phone number, you can't even save it.

this is hard.

Sephy