Apple / iCloud Double Charged

Hello, I would like to seek help in terms of being double charge from different cards of mine. Yes I admit I did have both cards for "Payment & Shipping" in April 2020 as I was using it to pay my iCloud monthly bill, but since then I made my other card as the default payment. So since May 2020 till July 2020 payment was charged only to my other card then in August 2020 both of my cards are being charged simultaneously. This is a redundant cost for me. I would like to contact the Apple Service chat help just that I could not figure out how but only lead me to call Apple. I just removed one of my card now from the payment & shipping so that in the future it will not automatically charged again or double charged. I am from Brunei and calling Apple is not feasible for me at the moment. I am seeking your help in solving this issue and to get refund from one of my card.