Paying for a car you don't own anymore

Netstar is ripping me off, i reversed 2 months amount of May & June, They did hybrid of 370.44 twice for July and August. when the guy called me from finance department in July i told them they can take the 370.44 of hybrid. and please cancel my contract because its ending of July. on End of august debuted R370.44 again i called to cancel my contract. i got a letter that it was cancelled. now i get an email of statement that im owing 688.90 its for what because i don't owe anything at netstar worse part my contract ended with them in july. even if i was doing a month to month why 318.50 to pay while i was paying 243.50. I dont own the vehicle anymore its not the first time writing a complain. Now this is going to far i think i must involve my lawyers. I have been calling from May to cancel my contract till today. its not canceled i being told of monies i owe which dont know off.