How to get a Picsart refund for an annual subscription not linked to Apple Account?

ApplePay is simple a middleman in the payment system. They don't actually have your money at any time. They just interface between your payment method and the vendor. The only time they would play a role in this would be if you had subscribed through Apple, but you say you do not see this in your purchase history.

https://support.picsart.com/hc/en-us/articles/360002232017-Subscribing-to-Picsart

I am not clear as to what you mean when you say the Gmail used to buy the subscription is different from your Apple Account. If a different account purchased this then any payments made through Apple Pay would have been through that account, not yours. Do you have multiple accounts?

Refer to this page for Apple Support features ➔ Contact - Official Apple Support

Select from the presented options until you find a solution for your issue, or see if there is a chat or phone call contact method offered lower on the page under “Get more help” (you sometimes have to narrow down the options multiple times before this is shown). If you do not see your issue, keep experimenting with any series of selections until you reach one that offers a chat session or a telephone call and get the representative to redirect you.

This support article has various country telephone numbers for contacting Apple for support and service ➔ Contact Apple Support - Apple Support For some countries look under “Other” listing at the end of the list. Not every country has telephone support, and phone numbers may only work when calling from the same country.

There are two ways of subscribing.

#1 Through Picsart. You deal with Picsart. This way has nothing to do with Apple.

#2 Through Apple. The subscription will appear in your purchase history list unless a thief has stolen your card number, or a Family Sharing member has made the purchase, or another person shares use of your card.

Then you select Request a refund for apps or content that you bought from Apple - Apple Support

Trial subscriptions may result in a charge unless you cancel the subscription at least 24 hours in advance. I would give it at least 2 clear days since the "24 hrs" business is not a clear definition to me. --> If you want to cancel a subscription from Apple - Apple Support

I already provided the contact information for Apple should you wish to confer with them about this.

If you are not seeing this in your purchase history, you may have subscribed directly though PicsArt and you would need to unsubscribe through them.