Q: when people call, they got a busy tone even though i do not use the phone. Whats wrong

Hey rolffsweden,

You might have Do Not Disturb turned on - I would check that first:

To enable/disable, tap Settings > Do Not Disturb. When Do Not Disturb is on, a "moon" icon will appear in the status bar.

or

You can enable/disable Do Not Disturb in Control Center.

 

from: iOS: Using Do Not Disturb

http://support.apple.com/kb/HT5463

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Have a great day,

Delgadoh