Switch the SMS permission settings of the assistant.

Change the SMS permission setting of the assistant. This is because you didn't give him SMS permission when you used the assistant, so he kept reminding you to give him permission to complete the change. Nowadays, many apps need to obtain various permissions of mobile phones, such as voice call permissions and address book permissions. If you can't use it without authorization, he will always remind you that you can use it only after authorization.

The reason why the new mobile phone can't be exchanged for an assistant to send and receive text messages

If you can't get a text message after using the change assistant, there is something wrong with your mobile phone. You can restore your SMS to the original SMS in the settings, so that if you use the change assistant under normal circumstances, the new mobile phone can't receive SMS, and you can change or debug it in the settings so that you can receive SMS.