If your phone is quiet for 1-2 days, suspect SIM cloning.

Sbaek rice
Professor Gam Seung-ju, member of the Nanny Association at Korea University
The easiest way for an individual to find out whether the USIM is a duplicate or not is
‘Jeryomyeon

Susu a
Cell phone too quiet for 1-2 days
‘Data presentation
[Subun]
Gam Seung-ju, Professor, Korea University Information Security School
In that case, you can suspect a SIM clone.
Data sheet