Incompetence & laziness!

I’m living in the UK since early this year. I’ve never had a contract with MTN! Now these dimwits requesting (via SMS), that I settle my account! They never mention my name, the telephone number in question or the amount allegedly due. There’s also no email address or name to get back to. I certainly won’t make an oversees call to clear things up. The number they do use to harass me, belongs to Vodacom in any case. I’d give zero stars, if there was that option!????