Product: Credit card

Please help this is a true tragedy : Back in XX/XX/2016 my bank ( Sunburst in Maryland ) offered me a " better credit card rewards '' than the one I already had to pay for my gas and my groceries. 
The person that offered me this credit card who I believe is one of the managers at that location at the same time suggested I close my personal account because that particular account was still joint with my ex husnband 's name which I personally did not mind but I agree to replace it for a new personal account without his name on it. 
The agreement was also to MAKE SURE all of the automatic payments, like my OLD CREDIT CARD, mortgage, insurance etc were all transfer to new personal account before closing the OLD personal account. 
He reassured ma all automatic payments were in fact transferred to the new account. 
Apparently In the " old credit card, there was still a balance of XXXX cents that this person that " HELPED ME '' was supposed to pay it off before closing the old account Well ... Apparently hi did not only left the old credit card OPEN which was n't supposed to be left open but the card was still trying to get the payment from the THE CLOSED account. 
When more that a few letter arrived last year saying I had an unpaid balance that was not being paid because the account was close I did n't understand nor did I had a clue as to what they meant or what was going on. 
So I finally went to Suntrust again to ask about this. At that particular Sunburst the lady at the Branch in XXXX Maryland said that in fact " I do n't have a credit card with those last four digits therefore there must be a mistake. 
This was back maybe in XX/XX/XXXX of last year. So I let it go. 
Well Suntrust tried to reach me again via phone about this and once I understood what was going on and that the old the credit card was in fact still open and trying to collect funds from that one account has closed without closing the old credit car or the automatic payments I went immediately to the branck and demanded to close that account and paid the unpaid balanced that this has cost me an incredible amount of grief. 
But this is not the real tragedy The real tragedy is be cause of this horrible mistake my credit score went down about XXXX points!!!!!! 
I ve been trying to reach the credit report people to please dispute this that this is not my fault. Sunburst now is claiming there is nothing they can do that nowhere is written something went wrong, they are saying basically this is my fault. 
Now the credit report automatically took average one hundred points because of this. 
This is a tragedy no one should ever go through. 
I work so hard to pay my bills on time, I ve never ever ever been late on any payments Please help The name of the entity is Sunburst Bank and the branch that had the person done this is in XXXX Maryland. The first name of the person that works at Sunburst that has made this error of neither closing my credit card nor transferring the unpaid balance to the new account he opened is XXXX The woman that said I do n't have that credit card on file and to let it go back in XX/XX/XXXX of last year was in XXXX Maryland on the Suntrust branch right of XXXX. 
Please help!!!!!! 
XXXX XXXX