Wireless phone not receiving transferred calls

[Frodo_Baggins]

Right subforum? 🤔

 

I've got some Yealink DECT phones, at school 1 they can make calls to and from the DECT phone but can't transfer calls to it - at school 2 they can do all of the same plus transfer.

 

Been looking at it for a while but not getting anywhere anytime soon, ISP is no help and 2 different phone support providers seem stuck on this.

 

Phone 1 transfers to DECT phone, phone 1 here's ringing tone but then after a few minutes gets the busy tone (the DECT phone never actually rings.)

 

Info: DECT phone is Yealink w73h, the phones are Unify VOIP phones on an openscape business phone system hosted over the wan at our central office with trunks\stun by voiceflex (both school 1 and 2 come to the phone server via the Fortigate on the same policy.)

 

Will hopefully be at site tomorrow to do captures and see what's going on, anyone seen this before?

Edited October 21, 2025 by Frodo_Baggins

[1TF0rward]

Only time I've seen this when one phone had the DNS set to just 8.8.8.8 it wouldn't get transfers as the other had the local DNS server set. May not be relevant but worth a check?

[Frodo_Baggins]

On 21/10/2025 at 14:54, 1TF0rward said:

Only time I've seen this when one phone had the DNS set to just 8.8.8.8 it wouldn't get transfers as the other had the local DNS server set. May not be relevant but worth a check?

Thanks, It's not DNS. I'm at site now and had a bit of mixed information from the technician on site. Turns out other VOIP phones can't call the Yealink phones either (Unify calls and plays dial tone but Yealink never rings)

[Frodo_Baggins]

As an update in case anyone has a similar issue, the packets were leaving the pbx server as 5070 but when they were reaching the phones it was 5060 and then getting rejected by the handsets

 

despite assurances from the ISP it turned out SIP ALG was enabled on the school's router, this has since been turned off and I'll be hopefully testing again soon.

 

If the packets are still being to the phone as 5060 then I'll probably just change the ports on the pbx and phones to 5060 as there's no point trying to battle the ISP and no way of knowing they have actually done what they said they had.