URGENT : AU CC 6K interest charged.

Last month bill was 14116 , Looks like somehow I paid 14k only ( i remember paying all, as I did multiple payments , may be some payment failed ,not sure.. have to recheck ) , so only 14k got credited to cc and this  Rs.116 is remaining...

Now , in this month's statement I see AU charged total 6K in interest+ gst.. I contacted customer care over call and explained and asked for reversal , he said he will raise request and some other team will check and update on reversal.

Guys, any suggestions ?  if any of u faced such issue with AU ,were you able to get reversal ?  should I also mail them ? Also this is first time something like this happened to me , any pointers are welcome..