Thank you for asking. To avoid any misunderstanding during this conversation, please provide me more information below in English.
1. Can this 4G service operate in other phone?
2. Your current firmware version. Also, please check if your firmware is the latest version.
#ZB570TL BIOS & Firmware Spothttps://www.asus.com/Phone/ZenFone-Max-Plus-M1/HelpDesk_BIOS/
3. Access "Safe Mode" to test the 4G service. https://www.asus.com/support/FAQ/1005163/
4. Please tell us your 4G service operator name. Is VoLTE enabled?
5. Have you tried changing the preferred network to "3G"? Does it improve the problem?
For further information, please check the link below. https://www.asus.com/support/FAQ/1011478/