SIP using BT HSIPT - Not able to call mobile numbers

[Input IT]

Can anyone please help I've been trying to troubleshoot this for weeks.

Basically since updating to V20 my users cannot dial out to UK mobile numbers, starting with 07 - everything else working fine, incoming, outbound to 01** numbers, caller ID outbound correct etc

When i try to dial out on any number starting with 07 (either 3CX app or T46U handset) i get the error prompt "You are not able to make this call please contact your system administrator for assistance"

On the dashboard i get this error related to the call:

Call or Registration to 07*********@(Ln.10000@BT HSIPT - AFS) has failed. sip:***************:5060;lr replied: Forbidden (403)
(******* number and IP address omitted)

I suspect it is a SIP error rather then 3CX although contacting OneCom (the SIP providor) about the issue, they just send me an outdated V16/V18 guide to setup the trunk and basically 'figure it out yourself' kind of attitude

 

[OlegR_3CX]

Hi there.
So in seem that your provider does not like something that the phone system send to them.
Can you maybe recreate the trunk as there can be the case where your parameters was modified and now they don’t accept the invite from the PBX.

 

[Input IT]

Hi there.
So in seem that your provider does not like something that the phone system send to them.
Can you maybe recreate the trunk as there can be the case where your parameters was modified and now they don’t accept the invite from the PBX.

I have already tried that, multiple times with tweaking on certain settings for testing too, its really grinding me down the amount of time I've spent trying to troubleshoot this issue, i may just sack them off an move to another SIP provider

 

[OlegR_3CX]

Maybe you could ask them to give you more feedback on the issue and not the guides so you could have it as a reference for the future and find the source of the issue.