HDFC Bank — Emi Rtn charge

Address: hyderabad

I have hdfc sal account and get personal loan from hdfc bank i paid every month emi 6244 but once i coudn't maintains balance in account and that time i was charged with overdue charge which is around 649. Now, after 1 month they charge me 236 rs for emi rtn charges. If i have already paid overdue charges then why hdfc is again charging with emi rtn charges.