King Price error costing me

I've been with King Price from 11 years and was rating it as the best because theyve never let me down, but this time i just realised why people are changing insurances. Im now owing Europcar because they sent the wrong return date of the car to them and now i havent reached 30 days and europcar terminated by rental before the date i was given by king price , I've been asking them to correct it and its now almost 10days they are not fixing it and my bill is pilling up they even have a nerve to tell me to return before my 30days and my car is still under repairs and once i go to Europcar they will want they money that they charging me daily as if i privately rented their car. King Price made a mistake but now its like they don't even know how to fix and this is all costing me. Never put your trust in one insurer for a long time, they start well but in a long run they do nonsense that will leave you in debts