I am changing a mobile (for our American friends: "cell") provider and have decided to take this opportunity to not migrate my old number but start afresh to get rid of all the spam. The trouble is, I've had that number for over 15 years and have no idea how many people and companies I do want to hear from have it.

So I concocted a plan to update my voicemail prompt with something like, "this number is no longer valid, please call XYZ instead".

However, the vast majority of my mobile communication by far - about 99.95% - is by SMS.

So my idea is, setting up one of my spare N900s with my old SIM and some app or a script or whatever that would automatically reply to any incoming SMS with a prompt to update their address book - and leaving it running for a year or so, or until the credit runs out, whichever comes sooner.

Now, I am aware of SMSCON but have no experience with it. Having read its wiki, I am not entirely convinced it is cut out for the job. I do not want to set up a master number and definitely cannot expect people sending me messages to include special codes in them. I just want it to autoreply to any incoming message with a predefined text. Kinda like an SMS equivalent of an "out of the office" email.

Any ideas? Before I take the SMSCON code and start hacking it into shape