Travelstart service is non-existant.

I made a booking with Travelstart for a flight that was on 29 June 2023. Due to an error in the Travelstart payment system, the booking was cancelled. I called Travelstart and personally checked with them that the booking had been cancelled. I then decided to use a different airline and book directly with them. Unfortunately, the money from Travelstart was still deducted from my account and I had now paid double for a flight. I contacted Travelstart and they told me to contact the airline and request a refund, which I did. The airline gave me payment and merchant references and the refund was put into Travelstart's account at the end of July. After numerous times of contacting Travelstart and being told the process has been escalated I tried to contact them today only to be told, the process is still in motion and they will escalate the query. So Travelstart now has my money as well as the airline's money and I am no closer to receiving my refund, even after 3 months of trying. The service is absolutely shocking and unfortunately, there is no manager to speak to, only a call centre. My next step is legal action.