Hi all,
We've got a few cellphones at work, and a few days ago a worker came to us with an unusual problem.  She was receiving a lot of calls and voicemails from people (all over NZ), who said that she had tried to call them.  Their CallerID units were showing her cellphone number as a missed call, so they were "calling back".

Now our user knew that she hadn't called anyone, and no-one else had access to the phone.  A quick check of the call log showed that no outgoing calls had been placed.  She was receiving up to a dozen of these calls a day.  To make matters worse, this cellphone is designated as our "emergency" phone, so she had to drop what she was doing and answer it each time it rang.

Thankfully, a few callers left some clues as to what was happening.  It appears as though a tele-marketing firm based in India was the source of the calls.  The international prefix is not displayed on CallerID units here, so it only displayed the "local" Indian STD code and then the number, which resulted in the CallerID units displaying "02127xxxxxx".  As the people out there hit reply, they would dial our number, and be confused and annoyed that we hadn't actually called them.

Is there anything we can do?  Or are we at the mercy of the tele-marketers using a different originating phone number?  We may have to change numbers for this user, as they are being bombarded with "return calls", which are wasting everyone's time.

Does anyone here have a solution, or at least an understanding of how CallerID works when international borders are crossed?  I've contacted Vodafone, but they are effectively out of the loop with this, and Telecom were unable to help.