I can do unlimited outgoing calls, i think the problem is only incoming calls, let me try to do two ring groups
I’m using SIP
Ok, so you use a SIP trunking with how much call simultaneous max?
Try to check if the second call presented to Asterisk from you SIP trunk and if it’s Asterisk which gives an hangup or you’re sip provider.
If the second call is not presented to Asterisk (no incoming call on Asterisk) Then your provider hangups this call.
If sip trunk, check if you have no incominglimit = 1 with type = peer or any call-limit = 1
Just an idea like that.
Again if it works from internal, it shoudl work from external. 
But what is at the other end, your ALLO GSM gateway?
If that’s the case then this is what is most likely limiting you to only one inbound call for the same SIM at the same time…
Have a nice day!
Nick
type=peer username=XXX secret=XXX fromdomain=XXX.com host=XXX port=5060 outboundproxy=XXX qualify=no nat=yes insecure=port,invite dtmfmode=auto canreinvite=no disallow=all allow=ulaw,alaw outboundproxyport=5070 trustrpid=yes
thats my actual incoming config, i haven’t incominglimit or call-limit.
idk if is cause of that but when i receive the second call asterisk shows an sip suscribe error, idk the limit of simultaneous calls because i never specify
By default, if call-limit is not specified then its value should be : 2147483647 
I think it’s enough 
I try to change qualify = Yes instead of No and check if this peer is registered
Why there’s no context in your config trunk for incoming settings / User Details??
Read this link :
https://wiki.freepbx.org/display/FPG/Trunk+Sample+Configurations
hello i added a call-limit to every extension and to trunk and i think is working now
Great.
Maybe the call limit was configured for a global settings somewhere and applied everywhere.