S10+ Preorder Problems

Hello, I'm hoping someone can point me in the right direction. I've been trying to preorder two S10+ online for days now. Four orders have been cancelled due to a "system error" I'm being told. I've talked to multiple reps online and

on the phone with no help. I was trying to upgrade 1 line and add a new line for the BOGO offer with the visa giftcard. The last agent at customer care told me to try on samsung.com which I did even though I wouldn't get the visa and I discovered the problem. The system is showing I already own an S10+ on the line I'm trying to upgrade and upon learning this I called customer care back and they're stumped on how to fix it. Any ideas?