Smsq sends many times the same message

Using Swisscom, the main swiss operator, smsq sends many time the same message (usually at least 6 times).

Example: smsq --motx-channel=‘Zap/g1/0622100000’ XXXXXXXXX ‘Hello World’

Asterisk logs:

Attempting call on Zap/1/0622100000 for application SMS(0) (Retry 1)
– Requested transfer capability: 0x00 - SPEECH
Aug 7 13:39:58 NOTICE[20641]: channel.c:2513 __ast_request_and_dial: Don’t know what to do with control frame 15
> Channel Zap/1-1 was answered.
> Launching SMS(0) on Zap/1-1
– SMS RX 93 00 6D
– SMS TX 91 16 05 07 0A 81 70 36 42 50 52 00 F1 0B C8 32 9B FD 06 5D DF 72 36 19 A7
– SMS RX 95 09 01 00 70 80 70 31 04 34 40 58
– SMS TX 91 16 01 08 0A 81 70 36 42 50 52 00 F1 0B C8 32 9B FD 06 5D DF 72 36 19 AA
– SMS RX 95 09 01 00 70 80 70 31 04 44 40 48
– SMS TX 94 00 6C
– Channel 0/1, span 1 got hangup request
– Channel 0/1, span 1 received AOC-E charging 0 units
– Hungup ‘Zap/1-1’

The example has generated the message twice.

Anyone has an idea how to send only once a message ?

Versions:
OS: Debian Etch
Aterisk: 1.2.13 (Debian package)
Channel: vzaphfc 1.2.11 (Debian module)