①? Go to SMS > More > Settings and select Restore Default Settings.
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② enter settings > application management > more (or menu) > show system processes, then select information, click storage, and then select delete data and clear cache.
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③ go to settings > advanced settings > backup and reset > restore network settings (some models don't need this setting), and then try to send SMS.
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Remarks: If the SMS sending function cannot be restored, please back up important data and restore the factory settings to try to solve it. If it still can't be solved, please back up the important data in advance and take the purchase invoice to Huawei customer service center for testing and processing.