Legal Question in Legal Ethics in Pennsylvania

The person who made the power of attorney (called the prinicipal) may revoke the power of attorney. Read the power of attorney document as it may specify how the power of attorney can be revoked. Usually, if it was filed at the courthouse/register of deeds, then a revocation has to also be filed. If the power of attorney was not filed then it is revoked by sending the revocation via certified mail to the agent.

If you simply added the person to the bank account, you will have to talk to the bank. Basically, you would have to open a new bank account and both parties would have to agree to close the account.