Synchrony Financial Credit Card Complaint

Synchrony Financial Credit card department,

Balance transfer Illinois

I had a Walmart store credit card until several months ago, Synchrony Bank upgraded my account to a Walmart MasterCard and transferred over my balance. Out of habit, I paid my bill through my bank 's bill pay and paid to my old account. When I realized what I had done, I requested a refund and submitted payment to the correct account. I received my refund check and deposited it. Shortly after, I checked my Walmart account online and saw they had taken the payment from the old account, sent it to the new, and I now have incurred a balance on my closed account. I try repeatedly to pay it off but it still goes to my new account, leaving me with this balance and interest charges each month. I have phoned them, left online messages, and have gone through an account investigation with them with no resolution and am worried about my credit.