Product: Checking or savings account

I was grossly overcharged for a transaction in XXXX XXXX XXXX Many, many attempts to resolve the charge with the merchant were unsuccessful. I was left with no recourse but to dispute the transaction with my bank, Santander. 
I called the dispute center and explained all that had transpired. I was told that an investigation had been opened and documentation would be requested from the merchant. Less than a week later I was mailed a notice claiming that the merchant had provided proof of the transaction and my dispute was denied. I called to exercise my right to be provided any documentation. I was told that nothing was received from the merchant. My claim was immediately denied by their system because the bank does not intervene when disputes are relative to the quality of goods and services. 1 ) The bank miscategorized the transaction, as I was disputing the amount, NOT the quality. 2 ) The bank notice misrepresented the actions taken. They did not open an investigation. They did not request or receive anything from the merchant. 
Again I opened a dispute of the same transaction. This second instance I made abundantly clear that I was disputing the amount, not the quality of the service. Again I was told that an investigation would be opened. Again in just a matter of days I received the same notice, verbatim. Again I called to exercise my right to be provided the proof detailed within the notice. Again I was told that no such documentation existed because the bank miscategorized the dispute and it was immediately denied by the system. Despite the clear bank error ( s ), the representative refused to open a third dispute. I asked to speak to a manager. She was extremely rude, refused to open and correctly classify the dispute, and hang up on me. 3 ) The bank miscategorized the transaction, as I was disputing the amount, NOT the quality. 4 ) The bank notice misrepresented the actions taken. They did not open an investigation. They did not request or receive anything from the merchant. 5 ) The manager was verbally abusive and unprofessional. 
I visited a branch with hopes for better treatment and handling of my dispute. I provided pictures, screenshots, notes of prior communications anything and everything related to my claim and their twice mishandling of it. The branch representative called the dispute center on my behalf. All documentation was submitted electronically. She and I were assured that the dispute was being classified correctly and an investigation would be opened. Again in just a matter of days I received the same notice, verbatim. 6 ) The bank miscategorized the transaction, as I was disputing the amount, NOT the quality. 7 ) The bank notice misrepresented the actions taken. They did not open an investigation. They did not request or receive anything from the merchant. 
I again visited the same branch to inform them that the same mishandling had recurred. She called for me and confirmed the misclassification, followed by an immediate denial by the system. She spoke to a dispute center rep at length and was eventually told that they were going to try again with special handling to ensure itd be managed correctly. Again I was told that an investigation would be opened. Again in just a matter of days I received the same notice, verbatim. Again I called to exercise my right to be provided the proof detailed within the notice. This time the rep did not inform me of what I already knew that there was no investigation nor documentation. He just told me it would be emailed within days. I pressed for more information because I knew he was wrong. He became insistent that there was documentation and thats why it was denied. I became equally insistent on speaking to someone with access to more information. I was connected to a supervisor named XXXX. She informed that the dispute was again electronically denied right away. However, this time it was classified correctly. The reason for the denial was that it was over the time limit ( 120 days ) for filing a dispute. 8 ) The bank erroneously denied the transaction due to time limit, as it was a refiling of a claim thrice filed within the time limit, which were denied due to bank error. 9 ) The bank notice misrepresented the actions taken. They did not open an investigation. They did not request or receive anything from the merchant. 10 ) The initial rep was incompetent, and rude on top of it.

I spent more than 90 minutes explaining everything that had transpired to XXXX. She was able to verify the scope of the mishandling by researching the 4 filed disputes. She took notes. I was instructed to again submit everything via email. I was told it would be escalated to her manager for review, and then brought to the department head for a determination. I was told I would be called the following Tuesday to be informed of their determination. Tuesday came and went with no call. I waited a week and again messaged to email address to ask for follow-up, with no response. Another week later I called to inquire. The first call resulted in me being told that there were no viewable notes indicating what was being done nor who Id spoken to. I quickly hung up and called back to try for someone more knowledgeable. The next rep connected me to supervisor. She said that she could see the notes and would contact XXXX to ask her to call me back. Two more weeks elapsed before I called in again. I spoke to XXXX for 50 minutes while she reviewed information and attempted to contact both XXXX and her manager. I was told that someone, either her or XXXX, would reach out by Monday. Monday came and went without any communication. I waited two weeks before calling in, again. I was told that XXXX would call me back. XXXX did call back. I missed the call, but her voicemail was not an update. It was another request for me to provide already-submitted and/or discussed information. We were able to connect the following day. After briefly expressing my frustration, she suggested a 3-way call with the merchant. I hesitantly agree, as I knew it would not be worth the time nor energy. The merchant made a final offer of compensation which amount to roughly 1/3 of the amount I was overcharged. I refused. The merchant dropped of and XXXX and I spoke. She informed that the bank would be unlikely to intervene because an offer was made. I refuted that logic on the grounds that the offer was only a fraction of overcharged amount. She said the bank had all they need and Id be informed of their decision shortly. Later that day she called to state that me dispute was denied for referral back to the merchant. 
I filed a valid dispute of a transaction on the basis that I was charged an incorrect amount. I submitted a great deal of evidence to support the claim as valid. After months and months of bank errors, misinformation, misrepresentation and general mishandling of the dispute, as well as my wasted time, effort and patience, the dispute was denied because the merchant offered to compensate me for a fraction of their fraudulent overcharge?!? There is no logical argument that can be made to make sense of such a decision. The bank failed to protect me as a cardholder per their own Terms of Service, as well as those of Mastercard.