Product: Checking or savings account

In XXXX, XXXX, I opened a " XXXX XXXX Checking Account '' with my then XXXX nephew who lived with me at that time. Since he was a minor I co-signed as guarantor of the checking account as required by San Diego County Credit Union. At that time, I was told by XXXX that I would only be responsible for the account until my nephew turned XXXX ( which, was only a month later in XX/XX/XXXX ). XXXX 's Truth-in-Savings Disclosure backed up what I was told in person by the branch representative : " The Teen First Checking account is for minors ( ages XXXX ). A parent or legal guardian must be a joint owner on the account until the minor reaches the age of XXXX. The joint owner consents and agrees to be the guarantor for any and all financial liabilities incurred through the use of any services, UNTIL the minor reaches XXXX. Teen First Checking accounts do not require eStatements. When the minor reaches XXXX, the account will be converted to a FREE Checking with eStatements account and will require eStatements to avoid a monthly fee. '' The moment my nephew turned XXXX the account was removed from my view on my existing online account ( for my own XXXX checking/savings ) and I could no longer access it. Based on the information provided to me in person when opening the account, the account disclosure referenced above, and the fact that I could no longer see or access the account details/balance/etc, I assumed and trusted that the account had been converted to my nephews own checking account with estatements. Fast forward a couple of years later : my nephew is now XXXX XXXX XXXX living in another state and has changed his address with XXXX. My nephew suffered a traumatic event and fell behind on his finances, and let his account become overdrawn. XXXX closed his account as a charge-off and reported it to both my nephew AND MY credit report. It was only at this time ( XX/XX/XXXX ) that I was notified ( by my credit monitoring, NOT by XXXX ) that XXXX had apparently kept me on the account as a 'joint ' checking and was holding me financially responsible. XXXX clearly had MY correct address and contact information, as I am a long-time upstanding client with zero history of negative comments from them on my own. XXXX made ZERO good-faith attempt to contact me to a ) let me know they had added me to a converted joint account that I could no longer access from my own online checking account ; b ) made zero attempts to advise me that this " joint '' account had it's address changed from my own to something in another state ( note, I was not receiving paper statements anyway, since their disclosure quoted above clearly says they give it " Estatements '' ), and c ) made zero attempts to contact me when the account was overdrawn and about to be reported to the credit bureaus. Had XXXX done any of these things, I would have gladly made an attempt to remove myself from the account ( and made a complaint at that time that their account disclosures are misleading and inaccurate ), and also would have offered to pay the account off so they could have their money prior to them ruining the credit of a perfectly upstanding client of theirs. So far, I have paid the negative funds in the charged-off account ( so the derogatory remark on my credit would at least be marked as 'paid ' ) and submitted disputes to 2 separate departments within XXXX. XXXX has refused to remove the remark, refused to acknowledge their account disclosure is inaccurate, and refused to acknowledge they made zero attempts to contact me at my address and contact information of record. The account in question was in good standing UNTIL my nephew reached the age of XXXX, and that was the only period I should be responsible for, based on the guarantee I agreed to while opening the account. *I do not even have the account number for the account in question, because it was not MY account*