After updating phone May 15, 2020 phone just only H+ sign... I have did all troubleshooting.
1. *#*#4636#*# - to LTE only
2. Restart phone
3. Factory reset
4. Change sim card
Thank you for your asking. Kindly provide the information below so that we could better assist you.
1. Your current firmware version
Setting >System>About Phone>Software information
If you try to update to the latest version, does the issue still remain? Could LTE and 4G work before update, and which version could LTE/4G work?
2. After you try change sim card, couldn't they works? Could you tell us the name of the carriers you've tried that have this problem?
3. Have you tried to open/close Volte?
Setting>Network & Internet>Mobile network>Advanced>Disable Enhanced 4G LTE Mode
4. What's your preferred network settings? (2G/3G or 2G/3G/4G)