Product: Credit card or prepaid card

Subject : Unfair interest penalty without any warning or notification! Financed {$6700.00} in XX/XX/2020, but despite paying ~ {$5000.00} in timely monthly payments, my balance is still shockingly at {$6500.00} ( 97 % of original amount ) I bought flooring from Lumber Liquidators ( LL ) in XXXX 2020. LL and Synchrony were running a financing promotion whereby i could finance {$6700.00} purchase through Synchrony card without any interest for 24 months. 
This was my first such financing transaction and i availed the interesting offer. I set up the autopay for minimum monthly payment that was decided by Synchrony, The amount was paid through autopay option every single month on time. 
I was under the impression that Synchrony would recover the amount timely through monthly payments and i set up the auto pay to ensure the monthly payments weren't delayed. 
However, recently when i checked my statement, i was shocked to discover that after paying about XXXX through the monthly payments, the outstanding amount was still {$6500.00}, almost equal to original financing amount. 
Apparently, Synchrony charged me {$4300.00} in Interest for the first 24 months also on the ground that i still had a balance of {$2400.00} at the end of 24 months. 

Date of purchase : XX/XX/2020 Subject : Unfair interest penalty without any warning or notification! Financed {$6700.00} in 2020, but despite paying ~ {$5000.00} in timely monthly payments, my balance is still shockingly {$6500.00} ( 97 % of original amount ) I bought flooring from Lumber Liquidators ( LL ) in XXXX 2020. LL and Synchrony were running a financing promotion whereby i could finance {$6700.00} purchase through Synchrony card without any interest for 24 months. 
This was my first such financing transaction and i availed the interesting offer. I took appropriate steps to ensure timely processing of monthly payments. I set up auto pay for the minimum monthly payment to be decided by Synchrony. The amount billed by Synchrony was paid through auto pay every single month on time. 
I was under the impression that Synchrony would recover the amount timely through monthly payments. Additionally, i set up the auto pay to ensure the monthly payments were processed on time. 
However, recently when i checked my statement, i was shocked to discover that after paying about XXXX through the monthly payments, the outstanding amount was still {$6500.00}, almost equal to original financing amount. 
Apparently, Synchrony charged me {$4300.00} in Interest for the first 24 months also on the ground that i still had a balance of {$2400.00} at the end of 24 months. 

This is totally unfair on the following grounds. 
XXXX ) I did not decide the monthly amount to be paid but the bank did. So, how come my minimum monthly payment amount was not set to ensure recovery of full amount in the first 24 months? Did bank set a lower monthly payment amount to ensure some balance does remain outstanding at the end of 24 months, giving them an excuse to charge a heavy penalty? 

XXXX ) Despite having my email and phone on the file, i was not informed by Synchrony that they are going to charge me {$4300.00} in penal interest if i don't settle the {$1800.00} balance at the end of XXXX. Their claim that they sent a monthly estatement isn't fair as they never sent a statement even through email, it was just an email notifying that the new statement is ready. 
In addition, as a responsible person, i opted for estatement ( caring for the environment ) and set up auto pay to ensure timely monthly payment. Therefore, i didn't really think of looking at the standard monthly email. 
If they had sent a letter, called me or even sent a separate email notifying me of such a huge charge, i would have immediately paid as i haven't delayed any single payment.