How to end management agreement ?

Letting Agents

My agreement with the managing agents states:

"The agent will be entitled to charge a fee at the agreed rate in respect of any tenant introduced by them, for however long that same tenant remains in the property (irrespective of whether the tenant’s occupancy of the property is continuous or not), whether or not the agent negotiates the subsequent extensions of the initial term."

I spoke with the Managing Agents to express my concerns with the service I was receiving but did not intend to end the agreement. However, my tenant contacted me directly (having obtained my number from a neighbour) to say how upset she was by the treatment she had received from the agent, that she felt bullied and intimidated etc and would prefer to deal with matters direct.

I am happy to deal with matters directly but where do I stand in relation to the management agreement I signed up to?

Thank you