Notice to cancel letting agent management

Letting Agents

hi

im wondering if you might be able to advise please? ... I currently let out 1 single property and there was a 12 month contract in place which expired 24 April 2020. However, the tenants have still paid a month in advance through the letting agents on 25 April 2020. The letting agents have been extremely poor in their management of the property and i would like to cease business with them. The letting agent did contact me in March to ask whether i would like to extend the contract with the tenants for a further year but i was poorly for a period of time and didnt get back to them as a result. The letting agents say i need to give them 2 months notice but i cant see how as there is no AST in place?

Would you know whether i have to give the letting agents notice or whether i can walk away without consequence?

many thanks
Danielle