Netstar is forcing their business on people

I had a car insurance with Budget Insurance, and this insurance included Netstar package (Agreement between Budget and Netstar) in order to provide clients with low premiums. I have successfully cancelled Budget Insurance and now I am liable for Netstar contract which I never signed up for. Everyday, I receive sms and phone calls stating that I owe Netstar, but, to my dismay, Netstar can't even provide me with a contract that I have signed authorising them to debit my bank account. I have also sent cancellation email and made phone calls to cancel, but no written response received from Netstar, except,calls demanding payment. Is Netstar trying to force their business on people or robbing poor clients?