I used Progressive Financing and had no problems with them. The store associate told me about the 90 days, but I also read through the contract because I noticed the biweekly amount that would come out of my account was only $70 and I agreed to $233.
I called Progressive before the first payment came out and made sure they set me up for the 90 days same as cash. You can also do this through the customer portal online. I realize everyone will have different experiences, but this is a finance company so similar to financing a car or anything else, they get more money from you the longer you have the balance open.
I would say just use this as a lesson to read through everything and follow up with questions as necessary. Also, make sure you do your own calculations to determine how much you should be paying each check to payoff your bill.