Trying To Get A Refund On A 12 Month Gold I Accidentally Bought. Help?

I was in gamestop a few days ago to buy microsoft points to purchase a game digitally on my consle, but I mistakenly bought gold. The employees told me there was no way to get a refund because they already activated the card. I then conacted microsoft who said they couldn't really do anything about it. I contacted gamestop and they told me that they sent a letter to the district manager who would look at the issue (in 3 to 5 business days) , and that I wasn't guranteed a refund. Is there anything I can do about this? Should I keep calling gamestop to press them to get me a refund?