Free Traffic Legal Advice

Looking for advice what to do next. For context I use the trust app to buy a monthly car park pass for the train station, which is what Saba advises to use. I received a PCN in April that I hadn’t paid for a days parking on 21st March 26. My pass was valid from 5th March for a calendar month. I appealed through their channels with a screenshot of my pass history. 3 weeks later they asked for further evidence that the pass was for that particular train station as it only had West Midlands trains on the pass. On the app the only monthly ticket available is for Wolverhampton train station all others are weekly. I screenshotted every pass available to show that and sent it to them. On 28th May I received an email to acknowledge receipt of the email with screenshots attached and said my account was on hold and would be in touch with any updates.
On 6th August I received a letter in the post from a debt recovery agency chasing the outstanding penalty. I have emailed Saba again to see what is going on and contacted the debt agency to say I’m still in dispute and will not be making any payment.
Any further advice appreciated