Yes, I tried almost everything.
- Unregistered and registered iMessage (Several times)
- Restarting the phone (Several times)
- Resetting the network settings (Several times)
- Contacted the (Carrier) customer care (Several times)
- Contacted apple support (3 times by now)
- Reset the whole iPhone (extreme step)
NOTHING has worked so far. I still see that red exclamation mark and message not delivered error.
Also, I inserted the same SIM to another Android and iPhone through which I was able to send both iMessage and Text message.
If I insert some other SIM to my iPhone I was able to send both iMessage and Text message to another number.
Basically, I am super confused on whom should I contact now? Apple Support or Carrier service...