Product: Checking or savings account

As a long time Citibank credit card customer, I received an offer to open a Citi Accelerate Savings in XX/XX/XXXX. I opened the account in early XX/XX/XXXX, funding on XX/XX/XXXX with {$20000.00} and receiving a competitive rate. I received a packet by mail requiring a W9 to be filled out, signed and returned. I sent it out quickly upon receipt in the envelope provided. On XX/XX/XXXX, my first statement cut and I noticed that Federal Withholding tax of  {$4.00} was kept out. I called Citi and was assured it would be returned upon receipt and certification of my W9. I am not subject to backup withholding and completed the form as such. 
On XX/XX/XXXX, my second statement cut and an additional {$8.00} was kept out for withholding. I called Citi again and was told they hadn't received my W9. I received a new form and mailed a completed and signed form on XX/XX/XXXX certified mail, return receipt ( at an expense of {$6.00} ). It was received on XX/XX/XXXX at Citi and signed for by an unreadable signature starting with XXXX  or XXXX. 
I contacted Citi again by chat on XX/XX/XXXX and was communicating with XXXX. He transferred me to XXXX for assistance and after about 30 minutes, I was escalated to a supervisor, XXXX. He said he would check into it and assured me it would be handled. He initially asked me to call back again to request the refund of taxes after he completed his review. After discussion, he agreed to call me back in a week. I never received further communication from XXXX. 
On XX/XX/XXXX, I chatted again with Citi and dealt with XXXX. She told me to call Citi and gave me a number to call in again. I did notice that my XX/XX/XXXX statement did not take out withholding and figured the refund would be coming. I decided to call again on XX/XX/XXXX and spoke with XXXX. She escalated me to a supervisor, XXXX, who gave me a lot of information. First, my original W9 was 'certified ' by Citi on XX/XX/XXXX and she told me my issue was shared by several thousand accounts. A fix was being worked on to refund the tax withheld in error, as well as account for any lost interest. This fix would be completed by XX/XX/XXXX at the latest. She also mentioned that she could find no notes or actions taken on my account related to the previous chats, calls and escalations. 
XX/XX/XXXX came and no fix was completed. I was becoming so frustrated, I considered closing my account, but decided to wait until after the holidays and hope the situation would finally be resolved. I called in again on XX/XX/XXXX and spoke with XXXX. She escalated me to a supervisor, XXXX. She acknowledged the certified W9 and said she had not heard of any other accounts being affected. She promised to correct the situation and took some actions on her computer, telling me the taxes withheld in error and the lost interest would be calculated and returned to me in 11 to 14 days. I waited until the statement cut again on XX/XX/XXXX and there still is no resolution. After spending many hours on the phone and chatting, in addition to sending another W9 at my expense, I still have not been satisfied with any refund, letter, proactive call or any proof that action has been, or will be taken. I feel that I have no other option but to turn to the CFPB for assistance.