Letting agent illegal charges

Letting Agents

I have recently rented out a property via a lettings agent for a 12 months contract where I agreed to pay 5% service fee for 1 year.
Following this I had another property coming in the market which I asked him to market. During the reference check it turned out that one candidate had reported false information about their employment and one of the guarantors had a CCJ on them . This left me with no choice other than cancelling their application .

Now this agent has deducted costs which I never agreed on from the rent of first property for the second property in prejudice and revenge .

What are my options in such matter as I simply asked him to market the property? No contract was signed or any costs were agreed on .

Thank you