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[andy]

Originally Posted by inquisitor

The SS7 protocol which is used for interconnection among carriers has a forward sequence number (FSN) and a forward indicator bit (FIB) by which the originating carrier discloses to the terminating carrier that a call is being forwarded and also from which phone number the call is actually originating. The main purpose of this information is that the terminal of the receiving party can indicate forwarded calls as such enabling the end user to distinguish between regular and forwarded calls (you might have noticed that your mobile phone indicates forwarded calls and displays the original callers number instead of the forwarding line's number).

Thanks for the explanation [shortened], and it does show as described.

Is it possible that they might block forwarding while a SIM is roaming - by which I mean here not on the home territory for the actual number being called - but allow it at home?

I suppose I can try this a bit more in a few days time