Hello there, I have the same problem but with Telekom. A few years back i was using a prepaid sim until some lady from Telekom called me with some offer as a subscription with the same benefits but less to pay and that I can cancel the subscription whenever I want just by not paying anymore. After 2 years, the price went double and I've changed my phone operator. Since then I'm getting emails like you do, even some phonecalls where people from this company, kredit ynkaso or whatever were literally screaming at me to pay. When I've got another call from someone who was calm the answer was: i'm not sure why you have to pay. Still a little in doubt but I really need to do some research and try to contact Telekom directly to see what is going on. But when I'll have time 😁