Cancelled new service+new iPhone within 3 weeks but taxes not refunded?

Hi folks, I recently signed up for a new T-Mobile subscription via phone and took advantage of the promotion where I got an iPhone 17 Pro. Unfortunately, my service coverage in my area is really poor so I had to cancel the subscription. So I canceled my service and shipped back the new iPhone within three weeks. I noticed that I don’t owe any balances however I had paid about $100 in taxes when I ordered the new iPhone 17 Pro. Customer service is telling me that I cannot get those taxes back because that’s already paid to the government. It’s really confusing to me because normally if you do a refund you get your sales tax back so do you know what I need to do to get that $100 back?