Nebula Took Money Giving No Info

I live in Dubuque, Iowa (52001) and I recently noticed an unknown charge from Vsa_nebulaap-og on my Cash App account in the amount of $51.48. The transaction appears as a purchase on my Cash App receipt dated June 5, 2006 at 1:14 pm. I did not place any order, did not approve any subscription, and do not recognize this merchant or what this charge could be for. After seeing this, I contacted the merchant. They replied that they could not find any person with my name (Pamela B***) or my email in their system, and that they had no record of a subscription or account matching the information I provided. They asked me to send a photo of the transaction so they could “fix this” if what I was saying was true, because they had no Pamela B*** in their system. Despite this, the $51.48 has already been taken from my account. I am requesting a full refund of the $51.48 and confirmation that there is no active subscription or recurring payment in my name with this merchant. I also expect a clear explanation of how this transaction occurred when there is allegedly no record of me or my details in their system. I want this issue resolved as quickly as possible so that no further unauthorized charges take place.