Microsoft Store Gift Card; with physical stores closed, how can I redeem them?

I have two old Microsoft Store gift cards (had received them as gift several years ago). They say on the back that "This Card does not expire", but they come with a 16-digit code which cannot be used at https://account.microsoft.com/billing/redeem because this page only accepts 25-digit codes. I know there was another thread regarding this issue, but that has already been closed and I cannot post there. The phone number that was mentioned there (1-877-696-7786) has not been of much help to me. When I call, the automated system asks about the issue I am having. The moment I say anything with "gift card" in it, it tells me to go online to Xbox website and seek help there. My problem has nothing to do with Xbox. I tried reaching out to Microsoft support through their Chat support, but the person to whom I was connected was not able to handle the case because it was out of scope for him. He also said that these card were supposed to be used at Microsoft Store and cannot be redeemed online. I responded by saying that there are no physical stores anymore, and that closing the stores does not relieve Microsoft from its financial obligations, and that it still has the obligation to honor these cards and provide a method to redeem them. But he kept repeating his statements. When I asked him to help me find the correct support team or forward my case to the support team that can handle this case, he became unresponsive and kept pasting a sentence saying that he sincerely apologized for the inconvenience. Finally, he asked if there was anything else he could help me with. When I asked if he could send me a transcript of the conversation, he immediately closed the chat window, possibly assuming that it would prevent me from being able to download the chat transcript. But I had already downloaded the transcript and just wanted to see his reaction. I was wondering if anyone here, from Microsoft support or otherwise, can help me with this issue. I had to choose the Gaming and Xbox as the product below, because there was no relevant option to my case, and because the previous thread was under this category.

:)