You can't withdraw money from someone's account whether you know the details or not. The person is supposed to sign a withdrawal check for you and then send the check so that you can withdraw the money here. Or he or she can wire the money through international wire transfer to a Ghanaian account number so that you can withdraw the money here. Better still the person can withdraw the money and then send the money to you through western union.
Note it is illegal to withdraw money from someones account unless the person has signed you a check. Before you can withdraw money from someones account, you have to know the persons account name, account number and then signature and if you are using atm card, you have to know the persons pin number. All the above information is illegal