Wakefields unprofessional levy collection process

Wakefields took over the property two years ago and I accidentally paid my levy into the old managing agents account. Both parties were advised and the funds transferred to Wakefields, one year later Wakefields re-debits my levy account for the amount. One year later I have not received any feedback on the arrears and all requests has fallen on deaf ears, interest being charged for over one year and eventually I have now received a final demand for the outstanding fees which they are unable to provide proof of or any feedback on how this was charged to my account after one year with no documentation or correspondence.