Product: Credit card or prepaid card

This relates to my Costco visa card issued by Citibank. On XX/XX/XXXX I made some purchases at Costco warehouse in XXXX, CT. Later I found that in addition to the purchases I recognized there was an extra separate charge of {$310.00} for goods bought here. Since I didn't buy these extra goods I visited the Costco XXXX warehouse on XX/XX/XXXX to see what this was about and seek a duplicate receipt for this supposed purchase. The warehouse folks ( including their back office staff that spent 30 minutes trying to find this out ) couldn't locate any such {$310.00} transaction that supposedly took place. They advised me to take it up with the credit card folks. So I then called this credit card customer service at XXXX who gave me conditional credit for this amount while they investigated the matter. 

On XX/XX/XXXX they notified me electronically that they have " closed out investigation and reversed our credit. '' The reason they gave was " This merchant has supplied us with a sales slip ( s ) indicating that this transaction took place in person and your credit card was present for this transaction. You should have received the merchandise at the time of the transaction ... '' I knew this form explanation was false because the warehouse people had been unable to show any such record of items purchased for this {$310.00} and I called uo the customer service at XXXX again on XX/XX/XXXX and spoke with their agent XXXX. 

XXXX then called the Costco XXXX CT warehouse while I was on hold and 30 minutes later confirmed that they had no such record of any purchase. He said he was re- reversing credit ( so I again wouldn't be on the hook to pay this {$310.00} amount ) while treating this as a fraudulent transaction that they would investigate. I hung up satisfied but then got the credit card bill of XX/XX/XXXX showing this charge of {$310.00} still on the bill, and no credit for it in the next ( current ) billing cycle. 

Today on XX/XX/XXXX I again called XXXX and after two failed calls, frustrating automated response system ( that kept saying " I didn't get your response '' ) I finally got through to billing disputes dept agent XXXX who said I would only get credit if and when their Security Department had completed their investigation ( she couldn't say when that would happen but could take a couple of billing cycles. ) Meanwhile the charges would stand on my account. As I understand it that's now how credit fraud charges are supposed to be processed. XXXX did say I was welcome to deduct these charges from the bill I was paying but there would be no proof from my side that such a conversation had taken place, so I'd essentially be liable for finance, etc. charges on outstanding carry over balances of amount owed. I asked XXXX if she could send me any communication ( email, text, etc. ) that I could offer as proof of her advice and she said she couldn't. 

In sum Citi Costco credit card dept first wrongly rejected my billing dispute on false grounds in their XX/XX/XXXX letter, and then wrongly refused to credit back the amount due on XX/XX/XXXX after opening the fraud investigation ( so I'm still on the hook to pay this amount for now. ) I shouldn't have to pay this wrongly charged amount while they take their own time investigating this matter. They should also fix their automated customer response system so that it works properly and doesn't make it so hard to reach a live agent.