Is it really not possible to prevent a call from being transferred by the calling party?


I need to (desperately) able to prevent a caller from transferring that call. So someone internal who places a call should not be able to transfer this. Incoming calls must still be “Transferable”.

I have played around with the t and T settings but that seems to prevent transferring through # or ## - our clients use the transfer option on the phones which is not caught by that.

After searching high and low, I am almost at the point that I think it cannot be done. Could someone shed some light on this?

Much appreciated.

You should probably limit the number of concurrent outgoing calls each extension can make and set it to 1.

Will upgrade tonight and post back if that solves the issue!


Nope that doesn’t do it. I just set up a test environment with freepbx 2.9, limited outbound concurrency to 1 on the extension but it still allows me to transfer the call I made. Thanks for the input though and in the process I discovered a new feature on 2.9!!

Any other ideas?

If the phone is not using the ## transfer method then it may be using some other method native to SIP and Asterisk. For example see these two pages:

Without knowing exactly how the phone initiates a transfer it’s impossible to say if what you want to do can be done. And even if you knew, it might be a question about Asterisk rather than FreePBX, which probably isn’t getting involved in this at. I’m not saying that there isn’t anyone on this forum that would know the answer (I know I don’t) but it might help if you would mention the make and model of one of the phones involved (because someone might know how they do transfers), and also, if you can watch the CLI while a call is being transferred and see what Asterisk actually does at the moment of the transfer, it might give you (or a more knowledgeable person) a clue as to how it’s being done. Armed with that information, the Asterisk folks might be able to tell you if it’s even possible to do the type of blocking you want. If it’s not possible in Asterisk, then it’s not possible in FreePBX.


Quite possibly the phones do use ## - what I meant is that they don’t physically press ## on the phone. It really is a variety of phones, but the most common ones are SNOM 300s.

The part that I am not getting is that from my understanding leaving out the T in the dial command options should prevent this.

As for the CLI: This is all I see upon a transfer, with 403 being the extension the call is being transferred to.

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