Product: Credit card or prepaid card

on XX/XX/XXXX, I signed a contract to have windows and doors installed at my house by XXXX. The total amount of the contract was {$12000.00} which was agreed to be financed under what the XXXX called " project finance terms ''. The project was to be financed for 84 months at either 7.99 % or 8.99 % interest rate ( I don't exactly remember now ). I was required to make monthly payments and have been doing so on time every month. Upon receipt of my monthly statement for the month of XX/XX/XXXX, I noticed a charge of {$2700.00} for " interest charge on purchases ''. I called the customer service number on the back of my " Lowes Advantage '' card issued by Synchrony bank. I was advised that I needed to call the credit department. When I called on XX/XX/XXXX, I was assisted by a representative from Synchrony Bank, who stated that this was not their issue, but a store issue for which I needed to visit the local store that completed the installation. I was advised by the same representative that for some reason, the project amount had been split into a two-thirds amount ( {$8600.00} ) and a one-third amount ( {$4200.00} ), and that while the two-thirds amount was processed accurately for the project finance terms, the one-third amount was processed under different terms at 24 months at 0 % financing. I called the XXXX corporate offices number and was told by a representative ( I will call " S '' ) on XX/XX/XXXX, that I needed to go to the store and request a " refund rebill '' in order for the correct promotion to be reflected on my account. On XX/XX/XXXX, I visited local XXXX store and met with the store manager on duty ( a Mr. XXXX XXXX XXXX ), who, told me that a " refund rebill '' could not be done as it would be too laborious and in my presence, called the credit department and then advised me that he was advised that I would see the correction within 2 billing cycles. On XX/XX/XXXX, I received an email with an attached letter dated XX/XX/XXXX, stating that my request for correction of this error could not be granted. No reason was provided as to why it could not be granted. On XX/XX/XXXX, I called the corporate Lowes offices and spoke with a XXXX " XXXX '', who again advised me that the correction would be made and I would see on my statement within 2 billing cycles. I did not hear back from any one at XXXX or Synchrony bank for 2 months. I called back on XX/XX/XXXX, spoke with XXXX " XXXX '', who kept me on hold for a very long time because ( according to her ) " somebody was working on the case ''. She came back after about 45 minutes to state that the request had been denied again, stating that it was a store error and that I had to go back to the store to seek resolution again. I advised her that I had been to the store already ad that did not yield anything. I then asked to speak with a supervisor and a XXXX " XXXX '' came on the phone and said " we can't do anything here about it. It was a store error ''. I then asked to speak with XXXX " XXXX '' manager and a XXXX " XXXX ''. came on to say the same thing that nothing could be XXXX and provided me a mailing address in XXXX, FL, as the next level of escalation, as well as XXXX corporate number, XXXX. On XX/XX/XXXX, I called XXXX corporate again, spoke with an agent who transferred me the local XXXX store where I had made the project arrangements. I was placed on hold by someone who said that she worked in the XXXX department and that my issue can only be resolved by a store manager. I was on hold for about 45 minutes and then the call was disconnected. The rime was about XXXX. I called back to the corporate number, spoke with a XXXX " XXXX '', who placed me on hold again and transferred me back to the same store, where a XXXX " XXXX '', placed me on yet another hold to get me to speak with the store manager XXXX " XXXX ''. XXXX " XXXX '' was unable to get the store manager and so told me that a XXXX " J '' will call me back from the store 's main line. At XXXX, XXXX " XXXX '', called me back and said that she would escalate this to her district manager, a XXXX XXXX XXXX At XXXX, XXXX " XXXX '' called me back and left a voice message stating that she was unable to reach her district manager and that she would call me back the following day. 
I have not heard back from anyone from XXXX or Synchrony bank since.