All you can do is put in a ticket to request the refund.
While they do work fro Blizzard, they are the moderators of this forum for the most part, and the forums themselves are not a direct way to contact support. Either to trouble shoot your issue with tech support, or to billing to request a refund.
I don’t see a post in your history where you asked in Technical support, and since we know nothing about your PC type beyond it has a NVIDIA card that is having issues, probably the Tech support forum would be your best bet to maybe try to trouble shoot this better, unless you have a Mac.
Lockups since 8.3 - Nvidia GPUs (Windows Thread)
Sadly it’s only affecting a certain set of players, with certain hardware and configurations. Reverting a patch that seems to be working for the majority of the players is likely not in the cards. Blizzard has it’s bare minimum hard ware requirements, but not all are going to play nice, and unlike console, you could literally have hundreds of configurations. While Blizzard gathers technical information from it’s users from time to time, to attempt to run test models in house to try to keep them compatible, it’s not always going to work out. Hate to ask, but have you considered getting a card from a different maker with a different GPU type in the mean time?