I think something similar happened to me a few years back. I used to raise DND complaints for the unwanted sms messages. And then after a while realised that important messages like OTP etc from some sources such as banks, traffic police etc were not getting delivered to me. Complaints to the customer care and appellate did not yield any solution. Then I managed to secure an internal contact and that person helped fixed my problem. I have no clue what he did, but I felt quite sure that its due to the DND complaints I raised for sms. Hence I stopped raising DND complaints altogether since then.