If you encounter Mobile Data network issues, don't worry. You can troubleshoot according to the specific fault phenomenon. Or contact realme customer service directly.
How to do with slow mobile network
How to switch between the main and secondary cards when using dual cards
Signal is normal, but it can't surf the Internet
Non-Internet secondary card steals mobile data
Unable to access the Internet with data network- How To Fix
Why hasn't the 5G internet speed improved?
If the above methods do not solve your problem, please back up your data and go to the nearest realme service center for testing.