Disappointed Client/Bad Client Service

I am disgusted by the service i got from Dollar Thrifty ....i had/have a query with them since December 2018 i keep on sending them emails to ask when they will sort out my query and all i hear is they working on it.I have a rental car from them since 11th December 2018 and i loaded my query 19th December 2018 and since then i keep on hearing they investigating and someone will call me,well it is almost a month later and NOTHING happend so far.I had to cut my holidays sort because of this.Before i rented the car they charged me a rate which i was satisfied with by the time i picked up the car i had to pay a diff.rate which was unexceptable and no one EVER did anything from their side i never budgeted for the rate they charged me when i picked up the car but had to cut some stuff to add that money to the rental because my holiday was booked and i had to go,but this is the worst service ever i got from a car rental and i rented from them since 2015.I had another booking from them in the month of January but i will def.cancel that because it is no use to rent from a rental company who does not respond to your queries,they might see it as nothing but it is something big for me because we had to pay for the rental way more then what we were charged.THIS IS BAD SERVICE FROM DOLLAR THRIFTY.