Wouldn't accept credit card due to billing address error, used my debit instead, both cards charged, how do i go about a refund for this double charge to my accounts?

When attempting to pat for my tax filing services, i got the error message that my billing address was not correct, i recently changed my address so i understand that. so, i attempted to use my credit card, which is not attached to my bank account. i received the same message. then, i proceeded to use my old address and it was able to advance to the next screen. i got notification on my bank account and credit card account that they were both charged. I wish to be refunded on one of those accounts but am unable to find any info on how to contact the company.