Synchrony Financial Credit Card Complaint

Synchrony Financial Credit card department,

APR or interest rate New York

I was at my - was - and my bill was high, they offered me carecredit company they said to me it 0 interest for 6 month and i did signed up. I was making payments every month but wasnt enough to finish all the amount i took from the card. After the 6 month 0 interest pormotion finished the company has charged me over - dollars almost - for the first 6 month which is the pormotion period. How come its pormotion and 0 interest and now they say cause i didnt pay in full before 6 month they charge me past 6 month which should be 0 interest. They scame they didnt explain this when i signed up for this card.