Car Rental from Planet42

The rental car I Received from Planet42 had a lot of problems, I rented it for 6 months but drove it for only 2 months because it had a lot of mechanical failures. The car was in and out of repairs for 4 months, I was basically paying for a car I was not using. Their communication with customers is bad, they reply to emails weeks later after sending multiple emails. I asked to return the car on the 6th month and they made me pay a cancellation fee on the 7th month. And now they are demanding payment for the 8th month.