No answer... No payment

Don't really understand their logic... I received an account from Lancet dated from December last year only in July this year. I made the effort and contacted the call Centre and told them I had problems with my phone and that they mustn't phone me only email. Anyway I paid some of the account to keep the peace and told them I need to argue some of the charges with the Med aid as there are double charges. I told them this and again a month had passed and I paid again on the account in August just to keep the peace. Now I have emailed to ask for the final amount to pay end of September and no one is getting back to me. Apparently being handed over. I am trying to sort out the account but getting threatened and no one answering me doesnt motivate me considering I have been double charged over again for the same stuff.