Credit card payments

Hi,

I had a credit card with Standard chartered bank with a credit limit of 30k when my outstanding was 20K, one fine day they suddenly reduced my credit limit to 17k and charged on excess on credit limit. Due to this I stopped paying oustanding amount after a long argument with bank saying before chrging for excess amount due to sudden change in credit limit i need to be given enough time. To my knowledge after 90 days of non pament accoutn has to be declared as NPA and stop charging interest, but they charged interest until it reach 1.90Lacs. Whether bank can charge interest until those many day nearly around 5yrs, any info would be appreciated

Thanks, Shiva