Charge a non-customer

My number was originally on contract for MANY years with MTN. I changed because of OVERcharges & Incorrect billing. I now happily use Telkom . Yesterday I received on this mobile a sms from MTN saying I've subscribed to MTN Fantasy Football ********** I'm a FEMALE PENSIONER & am NOT interested in football. I URGENTLY need an email reply IN WRITING to confirm that you will NOT charge me. Customer care numbers ring twice & click off. Writing to Customer Care gets only an automated response - they don't read the complaint. I DO NOT have a contract with MTN for this number - how do they do this? Obviously a **** by them to get more money out of people!!!!!!