Why does Apple's mobile phone generate extra international SMS charges?

When iPhone activates iMessage and FaceTime, it will generate an international short message starting with 0044. If the unlocked iPhone is used, the international SMS fee generated by activating the above services with China Mobile (U)SIM card in Chinese mainland will be reduced by default, and the related fees generated by locking and modifying the machine will not be reduced.

If it is confirmed that the requirements for activating the above functions are met, but the international SMS fee starting with 0044 is still incurred, please collect the following information according to Apple's requirements, and then contact Apple's technical support hotline 400-666-8800 for feedback.

(Note: The following information is essential). 1. Time and place of purchasing equipment; 2. Proof of purchasing equipment; Third, the photo of IMEI label is displayed on the back of the equipment packaging box; 4. When did the device automatically send international short messages? 5. If the equipment system is restored to new equipment, whether the problem still exists; Sixth, provide a complete "about this machine" screenshot.