Landlord help

It's a long story but I'll try to be concise. My landlord switched payment apps multiple times a year. The last one added a balance to my account. This was in 10/24. I immediately brought it to their attention. They didn't know how to fix but were "working on it". Every month we would get automated text and email. I would respond to them and then email the office that it was still an issue.

We moved end of 3/25. No contact from them. 7/25 I got a collection agency call. They stated that the landlord had sent a letter to my old address to a locked mailbox they had the key to. I asked for an explanation of the debt. They sent me a document that had rent amount but it's not the amount we paid & no dates. Late fees and then several months of insurance and pest control ( we had insurance and they had the copies of the policy. But they wanted to increase the amount of coverage needed during the lease but there was still more charges than it effected). Then they said I had to prove the debt wasn't real. I responded I needed to know the dates they are speaking about before I could prove a debt didn't exist but they are refusing from both landlords management company main office and debt collector. They are also withholding my deposit with no explanation. The collections supervisor said it was because I didn't give notice. My lease was non renewed by them. They gave us notice. I accused them of no renewal because I complained to management about safety issues with maintenance. They said no they were renovating the apartment. Which they didn't. So I was right it was retaliation.

This has been an absolute horror. But I saved every text, recorded call and emails. I have tons of proof. But I want them to say what it is first because I fear they will just keep changing reasons for the charges. What is my legal recourse with this.