Air India — Won't allow web check in and charging extra for checked fully paid ticket

My issue: For my flight with AirIndia PNR UVN7C9 I had four legs. Onward was ORD to DEL and DEL to BLR in late August. And return is BLR to DEL and DEL to ORD starting tomorrow. All 4 legs are on the same ticket. I took the flight from ORD to DEL and missed the flight from DEL to BLR during my onward journey due to bag delay. Now, they won't let me web check in to my return flight BLR to DEL + DEL to ORD. They said because I missed the previous flight I need to reach the airport 3hrs early to checkin at the counter and pay USD 300 as 'no show' charges. I have never done a 'no show' before and the terms and conditions on my ticket did not specify implications of missing a flight. I did not know that no show is not allowed.

Moreover, the AirIndia customer care was extremely unhelpful and they cut the phone in between when I was asking for help after spending 25+ minutes on call.

What I need: I am okay to reach the BLR airport early to checkin but I don't think it's fair for me to pay USD 300 as no show charges just to be able to board my return flight (if I did not have a return ticket they would never charge me this). I have flown international many times before but this is my first time with AirIndia and I had the worst experience ever.