Product: Credit card or prepaid card

Hello, Thank you for giving me the chance to submit my complaint. 

I have been going through a nightmare since I made order from Best Buy online. 
I ordered an All in One PC - For {$1600.00} including tax My order was for a Black PC however and because it was an open box order, the PC I received was not the right one and was even different color ( White ). That is why I took it back to Best Buy store in XXXX at XXXX  XXXX XXXX XXXX in XXXX New York. 
I went to customer service at the store and asked the agent if I can return the PC here or shall I mail it back as I received the wrong order and Its not the one I wanted. I was informed that I could return it in the store. 
He checked the PC to make sure all parts wer there. He turned it on to make sure it was working and asked if we have any personal data there, I said no. Then he took the PC and did the return and we got a return receipt. Then we have got the refund our Best Buy credit card. Also, we paid the credit card balance as we did order also a hard drive with the PC in the same online order but this we kept as there was nothing wrong with it. 
The Hard Drive was pickup at the store ( No problem was with that ) The PC was delivery to home ( This is the one we return ) {$1600.00} All was okay till after few weeks we saw new charges with the same amount of {$1600.00} to our card with no idea from where this charge came from and with no authorization from us. 
We contact Best Buy customer support to ask why this charge is in our account. They said we dont know as we see no problem here and advised to call the bank to cancel the changes as might be posted by mistake. 
We contacted Citi Bank and they asked us contact Best Buy and we have been between them going back and forth. We submitted a dispute for the charges as we were advised by Best Buy since this charge was a mistake. 
We did and the bank said we must wait from 4 to 6 weeks to get back to us by letter in the mail. We waited and got letter that we are responsible of the payment based on the evidence came with letter, and this evidence was just our online order invoice and delivery confirmation, nothing else about the new charges. 
We contact Citi Bank again and asked them how did this happen as we already returned this PC and we have a return receipt with us and we received refund for it already. They did not send us anything to clear the new charge. 
They said please fax or mail us the return receipt in order to reopen the dispute and they was so sorry about it ; however I did fax it and they reopen the dispute and asked us to wait another 4 to 6 weeks. 
We were so upset me and my husband but we had no choice and we was thinking this is the end of this issue. 
However, after waiting for a long time again they came back with same letter saying that we are responsible of the payment. We called to bank again as they didnt send us why this happen again. 
They however said on the phone that when Best Buy opened the box, the PC you returned was not the same as the one ordered, ( even they didnt mention this in the letter they sent us at all and we had to call them to know that ). This is the reason we returned the computer in the first place as it was not the right one. 
So we said yes therefore we return the PC because its not the same, its even showing on the return receipt under the reason of return that its not the one we wanted. 
So Best Buy took the PC from us and still charged us, how you even allow that? 
They said they would reopen the dispute and we had to wait for another 4 to 6 weeks. We said no we dont want wait again they said you have no choice however you can go to the store and talk with them to do a refund. We said we did already went before and the agent there didnt see the order we are charged for and he can not do anything, then the bank agent said go and talk to someone of the managers. 
So we went again to the store and asked to speak to a manager. We spoke with Mr. XXXX XXXX who did really good job trying to find out why this happen and the good thing is the agent we did the return with was there and XXXX asked him about the return. The Agent said yes, they did the return and there was no problem with it or anything unusual and then XXXX called the bank from the store phone to ask why I have got this charge and he inform them that I did return this order I got charge for, also he asked if they can get this done now and end this hassle, as the customer is very frustrated here now and for a long time already. The bank said no we must wait again, so he asked : Why did the bank asked the customer to go back to the store and you know we have nothing to do with that payment? The bank has no answer for that. 
XXXX was very sorry for us and said from his side he wishes if he can help or make a refund, but he can not see the order from his end to make any refund or cancel payment. 
He also advise us to avoid buying open box online and it is better to get it at the store, as it did happen many times this mistakes, as its good if we see the product in the store and try it before we buy it especially when it comes to open box items. 
He also gives us a return copy of the receipt and wrote on it that he sees no problem with the return, as I have also scan and will send with this letter, please see attached. 
So now we are waiting again, and we must wait for another 4 to 6 weeks. 
So our complaint here is against Best Buy and Citibank As for Best Buy : They did charge our credit card with no authorization from us and even never contact us to make clear with us anything before charging us for an order we already return at the store. 
As for Citibank : The company that manages the credit card, they should have acting against whomever charge dour card with no authorization from the card holder, and in fact they did not and even was helping to hide the mistake that Best Buy have committed against us. Which is against the Law and Credit Card Regulation. 
This problem is causing us me and my husband a big nightmare all this time since we did this order on XX/XX/XXXX Also did affect our credit score mine and my husbands credit score. My credit has always been Exceptional. During this whole ordeal, my credit card score has gone down 100 points. This significant decrease in credit has affected our life in so many ways. 
We are looking to get our right back from Best Buy and Citibank and let them pay us the most penalty possible to be an example for them to never do this with other customers out there again. 

The Order details : XXXX All in one PC Order date : XX/XX/XXXX Order Best Buy Number : # XXXX Last 4 numbers of the credit card used for the order : XXXX Card Holder : XXXX XXXX Please see attached with this from a copy of the return receipt with the store managers statement on it that the return was done at the store with no problems along with his business card. Also included is our bank statement copy and City Bank answer. 
Here is yours respectfully and sincerely, looking forward for your fair judgment, please do not hesitate to contact us if you have any questions or if there is anything not clear. 

Thank you Kind Regards, XXXX XXXX P.S- Also, we have not received all of the letters from Citi Bank regarding our disputes. We only received 2 and I think I made about 4-5 disputes with the last one on XX/XX/XXXX.