Product: Bank account or service

I made a purchase from an online merchant on XXXX/XXXX/XXXX as a holiday present. The merchant never fulfilled the order, despite contacting them via email on numerous occasions. I contacted Citibank in XXXX to contest the charge and sent in the requested documentation to open the investigation. Due to possible mailbox tampering at my residence and after not receiving a reply from Citibank regarding the investigation, I followed up with them in XXXX via phone and they told me to submit new documentation to reopen the investigation ( they had mailed me in XXXX, but I had n't received the letter ). I mailed Citibank the requested documents regarding the unfulfilled purchase and on XXXX/XXXX/XXXX was given a provisional credit for the purchase while they looked into the matter. I told all Citibank representatives that I spoke to that I was having difficulties with my mailbox at my address and travel frequently, so if they could reach out to me via email when they have updates on the dispute ( or need me to submit additional documents ) that would be preferable. After not hearing back from them regarding the dispute, I contacted Citibank and they explained that they 'd mailed a letter requesting additional information. As I had n't received their letter, I let them know that I could mail them the requested documents the following day. The representative said they would make a note on my case and they 'd extend the allotted time to submit this paperwork. I mailed in my additional documents the day after speaking with the Citibank representative. Citibank mailed me a letter on XXXX/XXXX/XXXX notifying me that they were closing the case since they had not received additional documents in " a timely matter '' and would be charging me for the provisional credit. I called Citibank again asking why they could n't follow up on the dispute as the last representative had told me that they 'd be extending the time permitting me to send in my additional documents. This Citibank representative told me to ignore the last letter sent to me as it was likely sent out before they had received my additional paperwork. On XXXX/XXXX/XXXX Citibank sent me another letter saying that they could n't do anything in regards to the dispute as all the requested information was not sent to them in a timely matter. I called Citibank again, this time speaking to an account specialist representative who, after listening to the entire ordeal, instructed me to resubmit all my paperwork to reopen the dispute. This representative gave me his name and employee number, but never a direct line to reach him ( all attempts to reach him after this time were unsuccessful ). Claiming to be my point of contact who would help me with this dispute, he made note that I travel frequently and may not see mailed letters until after the required date. He said that the dispute process can take up to 90 days, and I would be contacted if they needed further documentation. I mailed all requested documents to reopen this dispute on XXXX/XXXX/XXXX. I called Citibank today, XXXX/XXXX/XXXX, as I had not heard back from them regarding the investigation. They claimed that on XXXX/XXXX/XXXX they 'd mailed me a letter saying that they could not assist with the investigation as the charge is now over 6 months old. I demanded to speak to an account specialist who explained that they were obligated to reopen a dispute if I asked, however the dispute would always be rejected because I had n't submitted additional documentation back in XXXX XXXX when they 'd initially asked for it. In contacting Citibank on numerous occasions, I 'd received varied ( sometimes conflicting ) answers and in one case the wrong XXXX XXXX XXXX for submitting additional documents. Due to this, I 've spent a lot of wasted time, energy, and money in trying to combat a {$21.00} charge that they never intended to credit me for past my initial failure to follow-up in XXXX