Mio S20 User Manual page 22

No network service
SIM card can't use
Can't send SMS
Can't call or can't
answer the phone
PIN error
2. The battery wears,and the
performance will be gradually
reduced after using a few years
3. When couldn't get a signal,
phone will continue to launch to
look for the base station, which
will use a lot of battery, and
cause standby time short.
1. The SIM card is invalid
2. Not in a service area
3. Weak signal
1. SIM card is damaged
2.SIM card is not
properly.
3. SIM card contacts is not clean
Not open this service or no input
text message center number
Call limit has set
Input wrong PIN code three times
20
Replace new battery
Move to area of good signals or
shutdown for the moment
Contact with network operators
Check the network operator's
service area
Move to the window or choose
another service network
Back to network operators for
inspecting
installed To properly installed the SIM
card
wipe the contacts with a clean
cloth
contact with network operators,
and set the SMS center number
Close call limit
Contact with network operators