Tracker is not paying back my money!

I stopped using Tracker a few years ago and moved to another service provider for my cars. Tracker said I had arrears with them which I paid and cancelled the service. Now recently I was contacted by MCS Debt recovery stating that "my account" has been handed over to them for arrears, I told them that I do not owe tracker anything and they said I should discuss that with tracker. I then spoke with tracker and requested a copy of the phonecall of me signing up to that service. After a few days they contacted me and said "they" listened to the conversation and it their agent wasn't clear to what I was subscribing to so they will pay me back the money that was debited from my account. They took my account details and said it would reflect in 2-3working days. A week later I followed up because my money had not reflected in my account. They requested a letter from my bank confirming my bank account number, I gave that to them. They also requested POP of payment from my account for DEBIT ORDERS that happened in 2018, which is impossible. Now they have gone quiet on me. They're fast to take money and have issues paying us back!