I didn't receive the information feedback report when I sent a text message on my mobile phone, because?

The mobile phone can set whether to accept sending reports. If yes is selected but not received, it may be that the other party has not turned on the phone or is not in the service area. However, some mobile phones can't receive short messages in time when they are turned on immediately. Girlfriend's mobile phone is like this. She often sends several messages and receives them together.

As for how long it will take to get it without turning it on, I called Mobile and they said 24 hours, but I actually felt that it didn't take that long, as if it wouldn't work in an afternoon.