Contract Renew even without any talk and information after my cancelation

Dear O2 Team,

I am facing very bad experience of O2 Sales team. I canceled my O2 contract on 15-Nov and I got confirmation email also that from next month 15-Dec, your contract will be closed. 

However after 4-5 days, on 19-Nov suddenly I received e-mail from O2 that 

“wir freuen uns, dass Sie sich entschieden haben, weiterhin unseren Service von O2 zu nutzen.
Die vorliegende Kündigung betrachten wir als gegenstandslos und wünschen Ihnen weiterhin viel Spaß mit Ihrem Tarif.
Dessen Konditionen sowie alle weiteren Vertragsbestandteile finden Sie hier zusammengefasst.”

Not any person talked with me about any contract extension and renewal. 

its really very bad service management. I again cancled contract on 19-Nov itself. but today on 20-Nov morning again i receive mail from O2 that.. bla bla… terms and condition of your new contract. 

Dear O2 Team… Can you help me for that.. this is going on loop and I am not here to pay any extra money to O2 after from Dec onwards.