Gigaset E390 Manual page 57

The SMS is played back
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The "display call number" service is not activated.
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Ask the network provider to enable this feature (subject to a fee).
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Your mobile phone operator and SMS service provider are not working in partnership.
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Obtain information from your SMS service provider.
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The phone is not registered with the SMS service provider.
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Send an SMS to register the phone for receiving SMS.
SMS (text messages)
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