Mine was cancelled, too. I found out that AT&T did not accept the financing plan, even though AT&T shows that the plan is active and I am expected to pay it. I went ahead and order outright and will have to deal with AT&T. I am not sure about your situation, but thought I would share in case it helps.
I promise you that I don't mean this sarcastically, but.... GOOD LUCK WITH AT&T!! On the first day that pre-orders went live, I ordered an AT&T S20 Ultra, but for some off reason the $235 Samsung credit cleared out and didn't apply when I checked out. I did the AT&T finance plan and it charged over $400 on my credit card (tax for the phone and the $240-ish of accessories).
When I noticed that, I canceled my order thinking I could just place a new order. How very wrong I was! AT&T (Samsung I guess) placed the installment plan on my line, which in turn made no upgrade available. At that time, I tried to order again and use the Samsung financing instead. For some reason when I did, it wouldn't allow my full trade in value for my phone.
With that being said, I went into an AT&T store the next day to see if they could remove the installment plan. They called their customer service and they couldn't do it for some reason. They kept saying the installment plan was pending and they couldn't remove it yet.
Fast forward to 2 more trips to stores and multiple phone calls, and they still couldn't fix it. They all gave up so they opened a case with their "back office". They said it would take 3-5 business days.
5 business days later and it still wasn't fixed. I had to post on Twitter to get them to even acknowledge me. They did and the communication with that team starts. During this time I tried Samsung financing again and this time they offered full trade in value and I ordered the phone that way. Received the phone this past Wednesday, so it all worked out.
Meanwhile it took over a week for AT&T to finally remove that installment plan off my line.
Sorry for the long story, but it was a massive joke. The company themselves couldn't even remove an installment plan that wasn't supposed to be there.
Good luck to you and let me know how it goes!