I have been on 25k for 6 months and got the spend limit increased on June.I use around 2 to 3k monthly mainly paying some utility bills,fast tag sometimes on Zomato,BMS and occasionally phone recharge and Fresh to home :D
I had the same problem with idfc on Flipkart pay later.I emailed them with my cibil control number and they rectified it in 14 days.You can do the same.
https://www.idfcfirstbank.com/customer-care-sr/raise-a-request?cat=paylater&subCat=creditscore