Indigo Airlines — Bug in Indigo web checkin

Address: Mumbai City, Maharashtra

hi, I did my web check in Indigo mobile app booking one is X2LYRB.I was given automatic seat after web check in. I am quite confused when I am given some back aisle seat. When I called Customercare, they told o[censored] want to change ur seat, you need to pay for that. Could you please let me know what type of harassment is this? I am 100% sure there were no option of changing the seat. Please look the issue urgently. Thanks, Deb