a postal order from one of my titled relations

I have just received the text message equivalent of a begging letter, asking me to top up the credit on the sender's phone. This is apparently a new and exciting service offered by O2:

O2's brand-new service Credit Me lets one person top up someone else quickly and easily. So if you're roaming or just low on cash, you need never be out of credit.

If you are a Speak easy customer and need some credit, you simply send a free message to your generous parent or friend! Just type *108*08xxxxxxxx# and send.

Now a)the WHAT?, and b)I have no idea who has sent me this message - the number is not in my phone book, and it is unlikely that I would be on credit-cadging terms with someone whose phone number I don't already have. Though I now have detailed instructions on how to pay for their phone calls. Very odd.

getting irked now

Ok, this is getting really weird. Not to mention annoying.

I have now received five (count 'em, FIVE) text messages from Mystery Number A, asking me to provide them with credit for their phone. Then, just now, I received a text message from Mystery Number B, on a different network, saying that they have no credit and could I please call them?

I presume this is just a rather persistent case of mistaken phone number, though I'm not sure whether I should text them back or not. Either that or I have a stalker, albeit a rather impecunious one ("Sorry, I can't really afford to stalk you, can you loan us the price of a heavy-breathing phone call?").