How to get refund from Personal Facebook Ad Account

You have to first Deactivate the Personal Facebook Ad Account.

For Deactivate ad account, you will go to adsmanager.facebook.com --> Ad Account Settings  --> By default Ad account Setup selected --> click on Deactivate ad account

Now you open Payment Settings, you will see the message that Ad account pending closure. 
It may take up to 2 business days to complete this process. Once closed, you won't be able to run ads on this account.

When closed, then we get the option of refund in Payment Settings.