I recently received my first SMS scam message on my ancient mobile phone:
FREE MSG: Our records indicate that you may be entitled to £3350 for the accident you had. To apply free reply CLAIM to this message. To opt out text STOP
Do not reply to such messages. Just delete them.
The +44 prefix looks like it originates from the UK (where I live, therefore local number, therefore safe) but it’s actually a “personal number” that could be routed anywhere in the world, incurring high fees even for a simple SMS reply.
More examples of such scams in this F-Secure weblog post.