Huawei Honor 7 - Why DID My Phone Send a Message to an Unknown Number

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9.10 Why did my phone send a message to an unknown
number?
The messages that are sent by a third-party app not pre-installed on your phone will be
recorded and can be viewed on the messaging screen. You can determine whether the
third-party app causes security risks by viewing the message content.
9.11 What is the minimum length of a long text message for it
to be transferred to a multimedia message?
10 pages for China Telecom, China Mobile, and China Unicom.
9.12 What can I do if an SMS receiving/sending exception
occurs after I installed a third-party security app on my
phone?
The Android 4.4 system is added with a new feature to restrict the usage permission of a
non-default messaging app. It is recommended that you use the default messaging app for
receiving/sending SMSs. Go to Settings > All > Manage apps > Default app settings >
Messaging and select the default messaging app.