Synchrony Financial Synchrony Bank Deceptive, unethical / criminal business practices longwood Florida

My account with Synchrony was opened for $1,500, because i had major transmission work done and did not have enough credit cards to spread the enormous expense over.

They offered 12 months of interest free payment (30% deferred APR). I was paying down, on the average more than the minimum, on a monthly schedule.

On 4/14/2017 after 12 months and a balance of $786, had expired i was hit with a $459 interest charge. Now my balance went up to $1,245.

I immediately called them and asked why did they do that and they said that it was in their contract, which i never read since i opened this card at AAMCO transmission and all i had to do is sign on a screen to allow for credit background screening.  I never had or had the opportunity to read any contracts.  Also, no one ever discussed or disclosed that the interest will balloon at end of 12 months.

I asked to talk to their supervisor or someone higher up the org-chart and they said i need to call next business day.
I called several times between late April and June.  Each time they put me on very long hold times 1.5hours or longer as i tried to get in touch with their supervisor to explain what is going on.  Last time i called and asked to pay off the original debt and was put on hold again for well over 2hours.  I do not have time to wait on the phone for unreasonable amounts of time as i need to work and have responsibilities.

I called all 5 of my other credit cards and all the banks said that after their deferred APR expires normally the regular annual APR kicks in.  There is NO Ballooned interest with any of the other credit agencies.
I believe this bank is practicing unethically and possibly criminally.  I want to pay off my original debt in one lump sum and be done with it.