The metal
face of the
SIM card is
polluted.
Signals are
obstructed.
For instance,
radio waves
cannot be
effectively
transmitted
nearby a high
Poor received
building or in
signal quality
a basement.
Line
congestions
occur when
you use the
mobile phone
in high-traffic
hours
Clean the SIM card with a clean cloth
Move to a place where signals can be effectively transmitted
Avoid using the mobile phone in high-traffic hours
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