Holding my refund

I bought a car battery from Motus Ford Paarden Eiland. They charged me for the old one with the conditions that I must bring it back to get my refund back. I have called, no response. I emailed. No respond. Instead they keep telling me that they’re going to respond, but never do. It’s 6 days of me calling and emailing, and still no response. I want my money ASAP. This is unacceptable.