Huawei M635 User Manual page 35

The signal
strength is not
strong enough or
your phone is
often off line.
Your phone
displays "No
service found",
"Service
unavailable" or
"Network
problem".
• The antenna is in a good condition.
• Move close to a place with strong signal
strength.
• You are in an area with very weak signal or
outside your service provider's network
coverage (in a tunnel or surrounded by
buildings). If so, move to another area and
try again.
• Do not utilize the service option without
obtaining authorization from your service
provider.
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