Still waiting for my deposit

Good day rented a car with dollar thrifty ref number *** I've been waiting for my deposit since I returned their car. Nobody knows anything I've been transferred everywhere and when my call cuts noone bothers to call me back. Please assist I need my deposit my airtime runs out as noone picks up the phone or returns it when the call cuts off. This will definitely be the last time booking with them I am so sick and and tired of thi company noone gives a **** about my money. The car was returned with full tank I really don't know why it's so difficult to realese the deposit