Digitlogics — Flight Rescheduled

I am flying to Colombo.It was connected flight.
From Chandigarh to Delhi it was Vistara and from Delhi to Colombo it was Sri Lankan airlines.
When I came to India through same PNR it was perfect I got Boarding passes up to Chandigarh from Colombo.
But now on the way back Vistara refused me to give Boarding passes from Delhi to Colombo and used only up to Delhi.They rescheduled flight by 1.30 minutes without information. I just came to know when I reached counter.