The Piggybank is a fictitious account. This means that the balance shown in the Piggybank is not real money. Since the amount in the Piggybank is not real money, it is not possible to get the amount paid out or to withdraw it as cash.
Most people use the Piggybank to keep track of how much money the parents owe a child from un-paid allowances. If you are a child that uses Gimi, you can therefore talk to your parents about the best way to get the money your parents owe you. You can then deduct the amount you received from your parents from the Piggybank.