Incompetence of Lancet accounts department staff

I went for blood tests and the balance of my account was R57,30 in respect of which Lancet invoked a stop order against my bank account without my consent on 1 nov. 2017. Despite my having submitted numerous proof of payment documents i am harassed persistently for payment of this amount. Their staff's incompetence is unacceptable and makes me furious. I must say that this is not the first time that I had similar problems with them.