Unacceptable poor service

Please advise if I should be held liable to pay for a service that I was not told about. My cellphone contract were suppo to end last month, I received a call to upgrade around June which I declined because I don't want to continue with a contract, nevertheless the consultant to busy trying to convince me that I should consider renewing instead of respecting the customers wishes and to do their job effectively and with due diligence by informing us as the customers about procedures. They failed now they wanna force me to pay. Am I wrong to refuse.. For a mistake from them here im budgeting on that miney towards something else instead to mu surprise I receive an invoice.. ****** unbelievable