Mr Sultu, you may have missed some of the the fine print. Credit cards all over the world charge interest on the average daily balance of your current monthly statement. Even if you paid 6,000 out of the 8,277 owed you will still be responsible for the interest on the average daily balance for that month. I'm just sorry that the bank was not able to explain this in a way you understood. But let me assure you it is a standard practice (and no, I don't work for a bank, I've just owned credit cards for many decades.)
Mandi