How to switch Facebook Payment Method to Prepaid

Is it possible to switch from postpaid to prepaid or vice-versa?

The straight answer is "NO".

I don't have an explanation to elaborate for you but Facebook (meta) will not allow you to change its payment method from prepaid to postpaid it has to select while creating the Ad account. 

Is there a solution to this problem?  yes - the simple answer is to delete the exciting Ad account and create a new account in the Facebook business manager.

The Good News is you can change your payment type like if you want to change from a credit card to a debit card or vice versa you can or you can also use a net banking facility. This is the only thing you can change while paying for your Facebook ads.