Prefix (6994) added to specific numbers, not every time


We have an odd issue affecting two known phones, both GXP 2170s, for calling out.

About half the time, when either phone calls out, a 6994 is added to the front of the call, and the call connects elsewhere.

However, tracing these calls have been eluding me. Only the phone’s call history, (Edit:) and phone’s display during the call, shows the 6994 added, while the FreePBX Asterisk system does not (logs and CDR), which show the number exactly as it should, both when called correctly (without the 6994 randomly appearing) and when 699 is prefixed at the beginning. I’ve checked with our VOIP provider, and the CDR reports reflect the FreePBX’s logs as well, no 6994 prefixed.

Reviewed outbound routes and trunks (outbound VOIP, inbound analog, with fail over to analog, no mention of 699, just 8 to push calls out analog and skipping VOIP).

After having two sets of eyes reviewing the setup on one of the phones, we factory reset it, added the only extension, speed dials (none of which used when dialing), VLAN, header name for unique ringtone (transferred calls), and the DND’s feature code.

The Grandstream is on
PBX Firmware: 10.13.66-18
PBX Service Pack:

Other than the phone’s call history, I can’t find 6994 listed anywhere else.

Edit: Minor correction, 6994, not just 699.


Is that number 6994 in the caller id of the handset at all ?


Yes, on the Grandstream screen, the user will see 6994 prefixed (when it does happen randomly) after manually dialing the number and beginning the call (either already have the handset picked up and timeout is reached, or pressing the Green Handset/Orange Speaker buttons).


I’ve reached out to our VOIP provider, they also looked over the two FreePBX logs (good and prefixed), compared with their CDR reports, and not seeing any issues, as no trace of the 6994 shows up.

At this time, I’m not sure what other options we have to resolve this issue, as the prefixing happens when the number is dial and sent through. We could bandage the issue, however it’s not always the same number. I’m going to gather what all numbers it’s randomly prefixing, and see if I can find a pattern.


Before doing anything I recommend you update UCM to the latest FW, gradually passing through the various fw that have come out


Check the UCM extension Caller ID area of the handsets and remove 6994 from all entries.


Damiano, Kev - what UCM? I only saw FPBX.

In any event, look at the dial plan in the phone and see if there is something in that setting that is adding the prefix. You did not mention how or from where the phone is being provisioned. This is the only place that I can think of in a phone that can alter how a dial input entered into the phone can be altered when sent.

What I am uncertain about is how the phone shows the 6994 in the history, yet the FPBX log does not. However, I do not recall if the FPBX CDR logs shows the number as that which was received or as that when sent.

You can always to a capture from the phone and see what that shows as it does not lie.


Can it be history ?
maybe customer call once wring and now predictive call show him this option ?


As @lpneblett mentioned, what UCM?

The only manipulation of numbers, is at the server side, which is adding a 1 or 1-123 to certain numbers. With the exception of a call re-routing of going out the failover (analog) instead of VOIP, when the dialed number starts with an 8.

I agree with you, it doesn’t make sense that the Grandstream shows the 6994, but no signs of it in the FreePBX logs, CDR, or our VOIP Provider’s CDR reports. At one moment, I thought the call was failing over to analog, and manipulated there, but realized both test calls showed up in our VOIP provider’s CDR report. I’ll re-review the two logs I snatched out, to make sure something unusual with the analog happened, just to be sure.

The phone we’re focusing on for finding the fix, before jumping to all the phones or only affected phones, has been factory reset and fully updated. Though we cleared the history prior, thinking like @Marcin suggested, the factory reset cleared it too. At this time, I think we can rule out the Predictive Dialing from History. There are other categories for predictive dialing, however none are utilized to my knowledge, including the address book.

The only settings I implemented back into the phone:
Single user Account (Name, Display name, extension, secret, server IP, feature code for VM)
Speed dials and Parking (BLF extensions of all phones, small client of 24 users)
One Feature Key change to toggle DND (When mic mute is pressed, not in a call).
One Header/Alert code for a change of ringtone, meant for calls transferred to the phone.

The FreePBX isn’t setup complicated. Other than time conditions, all calls ring in, hit a recording then voicemail at night, or ring all during the day. Outbound calls go out VOIP, if VOIP cannot be reached, fails over to Analog, which is an aging Audiocodes device, planned to be replaced with a Grandstream FXO.
They are not on PJSIP, they are on Chansip. If Chansip is the issue, and I’m not sure where or how, I have 6 other client companies setup with Chansip.
Sidenote: I haven’t done any updated research on PJSIP in the last few years, but my boss wanted to stick with Chansip, due to BLF issues.

As for the capture, are you referring to a packet capture? I’ve done that twice, and can’t say I’ve mastered it yet. I have a team member who I can refer to for assistance.


Packet capture.
Start make such call, stop and download. You can post here or directly via PM to check.
Most advanced users can easy read it.


@lpneblett sleep deprivation, insomnia and old age comes into play, however in all asterisk based pbx’s the cid is something that can be programmed, FreePBX is just another variation of the UCM both of which use Asterisk at its core.


Depending on when the client’s employees are in this week, and how my schedule keeps adjusting, I’ll reply some time this week with that. Thanks!

Thanks for the translation/reference explaination. I’ve been working with phone systems for only a few years, and can’t say I picked up that reference. The FreePBX is up to date. At least once a week, when I’m remoting into the servers, I check the Module Updates page. On a side note, the server is set to reboot once a week on Sundays.