Product: Credit card or prepaid card

On XX/XX/XXXX, a 3rd party made a payment of {$3000.00} to my Discover account. I called Discover on XX/XX/XXXX at XXXX to confirm how long it would take for this money to post to my account, the associate from Discover informed me that when a payment is made on an account, the funds become available immediately, as Discover credits your account with the money, however it does not actually post to the account until 8 business days later. I called Discover again on XX/XX/XXXX at XXXX and confirmed with an associate that the {$3000.00} was indeed posted/cleared to my account and available for spending. Yesterday, XX/XX/2022, I opened my Discover account to see that the {$3000.00} had been marked as a " Returned Phone Payment '', and dated XX/XX/2022, which resulted in my account being in the negatives and stating that the amount I now owe to them is {$3700.00}. My previous balance before this was {$730.00}. I called Discover on XX/XX/2022 for an explanation as to why and when this returned payment took place, the representative stated that the payment was returned on XX/XX/2022, and the reason given was due to it being an " unauthorized transaction '', even though when I review my statement it says the returned phone payment occurred on XX/XX/2022. I explained to her the steps I took before spending any funds on my account, which included calling Discover and speaking with someone who confirmed that these funds were indeed available for spending. I have not received any communication via email, telephone, or mail informing me of any issues regarding this payment being unauthorized, and after speaking with a Discover associate that informed me on XX/XX/XXXX that the funds were in my account and available for spending, I had no other reason to believe that there would be an issue with this payment. Also after being told by Discover that the window of time for a payment to post on your account is 8 business days, now I am being told that it can take longer in special circumstances. I asked her to reference this call that I had on XX/XX/2022 that I mentioned above, however I was transferred to her supervisor and not provided any assistance with resolving my issue. I spoke with the Customer Payment Verification department and he states that this is an odd circumstance and the only way for the funds to be replaced is by the account that it came from. After receiving little to no help, I reviewed my cardholder agreement which states " If a third party makes a payment on your Account and we return all or a part of such payment, then we may adjust your Account for any amount returned. We reserve the right to defend ourselves against any demand to return funds we have received, and may agree to a compromise of the demanded amount as part of a settlement. '' I called Discover again on XX/XX/2022 and spoke with the supervisor of the customer verification department. After explaining my concern to the supervisor regarding the policy from their cardholder agreement ( referenced above ), the window of time I was given from Discover for when a payment has officially been cleared in my account, and the lack of communication on Discover 's behalf to me as a consumer, I was told that the only way to resolve this issue is through the third party and Discover can not assist. I have never spoken with the 3rd party 's bank account that submitted this payment of {$3000.00}, only Discover had communication with them.