MakeMyTrip India — H6R3QI - unable to use credit shell

I have a credit shell amount of rupees 2147/- with Spicejet that I want to use for a fresh booking to travel on the 15th of December 2020 on SG-310, Bangalore to Mumbai, for the same passenger.

When I go to the reschedule option, it is only allowing me to make a fresh booking for 2 passengers. The second passenger has already completed a preponed flight on the 20th of March 2020 with a different PNR (O8958S), hence this credit shell does not apply to him.

Please allow me to use the credit shell for a single passenger who did not fly, rather than for two passengers, one of whom has already flown.