I have a Redmi 9A Sport. It is unlocked: I have used it with 5 different SIM cards in different countries. The last SIM card was an MVNO (US Mobile) on the T-Mobile network.
I now have a SIM card from a different MVNO (Helium Mobile), also on the T-Mobile network, but the SIM fails to connect to the network. I tried the SIM card on another unlocked phone and it was able to connect to the network, so the problem is not the SIM card.
I checked the LTE bands and my phone has 1, 3, 5, 8, 40, and 41. T-Mobile has bands 2, 4, 5, 12, 66, 71, and it acquired Sprint, which had bands 5, 25, 41 (ref), so bands 5 and 41 are common between the phone and T-Mobile.
What could be the problem with the SIM card not connecting to the network, and how can I fix it?
