Misled Tenancy Agreement

Letting Agents

Hi
I have a dispute with my agent, who let my property on a fully managed service. Recently I have found out that it isn't an AST type agreement and in fact a company contractual agreement, which I have never signed or agreed to.
The managed agreement with the agent is due to cease on 15th December but they state that they are legally obligated to deducted 6 months commission payment from the final rent payment, which I have told them I don't agree to beacause of their breach.

There are also other issues and quite a few other breaches, but I would like to know where I stand with this initially as I don't want it to get confusing. I have contested it with the agents, but they are refusing to accept liability
Is it possible to request a letter template for me to send to the agents
Many thanks