Payment Reminder But I'm Not A Customer

I was sent a payment reminder on WhatsApp from Rain 20 minutes ago addressed to Katlego. I responded saying that I have never had a Rain account and that my name is not Katlego, and that he/she gave them the wrong number. I got a generic business reply.

I also received calls from a number I don't know on Monday (20 November), which I didn't answer. I just Googled the number now and, sure enough, it's Rain! Please stop calling me about a stranger's account, and please unlink my number from their account.

Thank you.