The new system is not even in place yet for broadband, but we had our first PSTN slamming today. In theory the PSTN side has been in place for some time, but it was very rare and we had a much less automated system in place before now. The new migration process means we have integrated our automated systems for PSTN lines as well as broadband.
Some other telco was trying to take over one of the PSTN lines that was part of an Office::1 installation. Our new system alerted the end user by email to their accounts and technical contacts and also texted them.
Unusually, it also alerted our sales staff as it is an Office::1 line, and transferring or ceasing one part of an Office::1 line is suspicious. The system has a few safeguards in place to try and pick up things like this.
Office::1 is a package of two or three PSTN and broadband lines with a FireBrick and optional 3G fallback providing a bonded and monitored service. Ceasing or transferring just one part of that service makes no sense, so will almost always be a mistake or slamming.
Needless to say the customer was pleased to be advised, and quick to confirm that he had not authorised a transfer.
Now we await our first broadband slamming - something that simply could not happen with MACs. Our what joy.
P.S. As someone asked on twitter, yes, you can pre-emptively tell us you are not planning to transfer so we reject a request (anti-slamming). It is on the control pages for your line.