Bad service of an estate agency

The estate agency Infinity Vest was my letting agent for my apartment. The letting agents decided that they do not want to let properties anymore, but rather sell properties. He they put the landlord, which is me, and tenant in contact with each other to do business on our own in future. This works well for us. The problem is: the tenant paid a deposit to the letting agent and the letting agent does not want to speak to the tenant anymore and has made it my problem to get the deposit back. I have to pay a lawyer to get the money out of the letting agent on behalf of the tenant.