Not getting reply or refund because after selling my car I am NO LONGER A CUSTOMER?

I sent the following to various people in the business, and logged the complaint online to which the response has been nonexistent or completely lacking in progress.

I have a complaint to make regarding a transaction I did with your branch in August / September of 2016.

I sold my Honda Jazz to your branch through Dylan the pre-owned car manager.

At the time we had to settle the vehicle and there was a shortfall on the offer from your branch which I had to pay in as the difference. There was a further calculation of shortfall based on the second set of keys for the vehicle.

At the time we resolved the figures and I paid in the difference, then there was a month end and another payment went off my account for the vehicle loan. The settlement figure had then changed. There was then a difference between the total I had paid in and the total settled with the bank in my favour.

I contacted Dylan to calculate and confirm the amount to return to me. He committed to getting back to me.

During the rest of the year I chased Dylan myself for a response and got a repeated commitment to get back to me. Eventually when I spent time for an entire day calling him repeatedly I got him in a meeting and sent him an SMS instead. The conversation which followed by SMS had Dylan clearly tell me that I was no longer a customer as the transaction was completed and he would only get back to me when he had time. I complained that this was not an appreciated level of service and he repeated the above description of my status.

He did commit to investigating and replying.

I followed up every now and then with no further response from him at all and I am still out of pocket for the difference.

I have been more than patient. I want this matter resolved urgently, if there is no amount due to me then I want a statement to that effect since my calculations show that I should have a return. The lack of customer service is something I expect you to resolve internally, I have no interest in being involved unless this communication and complaint has the same level of response as I have experienced so far.

After being contacted by Thato after I laid a complaint through the allowed channels on the website I gave my description of events and then Thato also disappeared.

I laid another complaint through the website and have had no further response again.

If I stop being a customer, of which I have had dealings with Honda and Honda vehicles for the last 10 years, then how does this reflect on the brand, or is it just this branch?

And the money I am owned? Really, is this a good way to do business, to have your "not a customer" out of pocket for months...