Synchrony Bank Credit Card Complaint

Synchrony Bank Credit card department,

Overlimit fee Florida

I have a Walmart Card with Synchrony Bank. When I opened the credit card I had a balance of $500.00 in 2014. I was offered not interest on the card for 3 or 6 months. I paid my payments each month, and I also paid off my balance. Every time I paid the full balance, I got a letter from Synchrony Bank stating that they reviewed my credit report, and due to my score they will need to lower my balance. They did this each time I paid the full balance. My credit balance went from $500.00 to $100.00. When they first changed my balance, I did not know, and they lowered my balance below what I had charged. This change in my balanced cost my payment to change from $25.00 to $30.00. When I received my next bill, Synchrony Bank had charged me an additional late fee. I do not understand how a credit card company can practice Re -pricing based of off unrelated accounts. I truly believe I am being discriminated against because of my race, and because I continue to payoff my balance on this card.