It seems that the provider is not able to recognize the codec

[sonoio :)]

Problem with the codec not recognized
Caller

INVITE...

v=0
o= ...
s=SIP Call
c=IN IP4 ...
t=0 0
m=audio 55158 RTP/AVP 18 8 0 4 3 125 101
c=IN IP4 .....
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=yes
a=rtpmap:8 PCMA/8000
a=rtpmap:0 PCMU/8000
a=rtpmap:4 G723/8000
a=fmtp:4 bitrate=5.3;annexa=no
a=rtpmap:3 GSM/8000
a=rtpmap:125 X-CCD/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
<------------->

== Using UDPTL CoS mark 5
Sending to ...:5060 (no NAT)
Using INVITE request as basis request - 20CC58DD-
C90411E0-97BAA52A-99A453FB@1....
Found peer '7' for '353851429967' from ...:5060
== Using SIP RTP CoS mark 5
Found RTP audio format 18
Found RTP audio format 8
Found RTP audio format 0
Found RTP audio format 4
Found RTP audio format 3
Found RTP audio format 125
Found RTP audio format 101
Found audio description format G729 for ID 18
Found audio description format PCMA for ID 8
Found audio description format PCMU for ID 0
Found audio description format G723 for ID 4
Found audio description format GSM for ID 3
Found unknown media description format X-CCD for ID 125
Found audio description format telephone-event for ID 101
Capabilities: us - 0x80030c7fffff (g723|gsm|ulaw|alaw|g726|adpcm|slin|
lpc10|g729|speex|speex16|ilbc|g726aal2|g722|slin16|jpeg|png|h261|h263|
h263p|h264|mpeg4|red|t140|siren7|siren14|testlaw|g719), peer -
audio=0x10f (g723|gsm|ulaw|alaw|g729)/video=0x0 (nothing)/text=0x0
(nothing), combined - 0x10f (g723|gsm|ulaw|alaw|g729)
Non-codec capabilities (dtmf): us - 0x1 (telephone-event|), peer - 0x1
(telephone-event|), combined - 0x1 (telephone-event|)