Hi kinsuk:
You can also send an e-mail message to: stefan at gtrvideos dot com
I had a problem in the past when trying to pay at Stefan's site using a credit card. The card was not accepted for the purchase. After contacting them, one of the staff got back to me, saying that the card was rejected on their end by the credit card issuer (MasterCard). I called MasterCard and they told me that it was flagged as "Unusual Activity" because of the distance from where I live (the Seattle, WA area in the U.S.). They made some changes to the security settings and when I tried again, the card was accepted. So, to make a long story longer, perhaps a call to your credit card issuer is in order to check on the problem. They should have a record of transactions, even those that were not completed.
It struck me as strange because I had made other purchases from companies as far away from here as Stefan's business in NJ. But with computers and AI running the show in background, I guess anything is possible.