Unethical business practice

My mom's car went for a service on 8 Jan. They swiped the card twice as the first time it was delayed even though we got an sms that it went off. A second amount went off and we've been struggling since then to get the money reversed. The amount is R4958.46. We've spoken to the manager in person. We've called. We went to them yesterday because they said we need to bring them proof. They told us they would call us yesterday but we haven't heard from them. My mom is a pensioner and this is extremely unfair on her costing money to follow-up all the time. We actually don't know what to do anymore because even the managers are not helpful. I'm wondering if they are drawing interest from the money sitting in their bank account. How unethical.