Upgrade

We financed a home repair project through Upgrade because of the interest-free option. That part went okay. Then before the project was fully completed, I began receiving emails about setting up my account and making payment. So I set up my account. Then today, when the last of the project was being finished, I received a phone call from (supposedly) an Upgrade representative. Opening comment: "Before I can tell you why I'm calling, I need to verify the last four numbers of your SS number." I asked why they were calling when the project wasn't even finished. He said "I can't tell you why I'm calling unless you give me the last four of you SS number. " I told him I wasn't going to do that since I didn't know if it was a scam or authentic, could he at least give me a ballpark topic, that would be helpful. He refused and again insisted on the SS number. I refused, he said well, call your contractor or Upgrade.
I called the contractor -- she said she had no idea why they would be calling as everything was in order on their end. I went online to set up my account. The website is VERY intrusive. The payment option screen required me to give access to my bank account, which is understandable, but then there was a "warning" that they would have full access to my account, transactions, account owners, and more. Perhaps if they had worded this warning differently, it would have been less intimidating, but with all the scams out there today, we have to look out for ourselves.
So I called Upgrade and explained that their website payment system seemed very intrusive and I preferred to just mail in my payments. She was insistent that I needed to pay online, that it took weeks to process check payments and they couldn't guarantee the check would be recorded by the due date. She also informed me that they had all of my bank information, etc, even though I stopped before I reached the "Confirm" button. I asked how they got that when I had not completed the setup procedure. She said "you must have hit "confirm". I again asked for information to send payment in by mail. At that point she (already speaking impatiently) became rude, condescending, and again insisted that I must pay online.
So I hung up on her. I was my company's bookkeeper for years. I pay all my bills online, I' m familiar with the process, I am not stupid as she inferred by her tone of voice, and I've never worked with a website that was so clear that they could access any information in my account.
At this point, I have no idea if my information is safe through their online system. Not happy AT ALL with this company's treatment of customers.