1 month arrear, Rude consultant refused to accept my payment arrangement

i had financial problems in September and which forced me not to pay my vehicle account, a very rude lady from MFC called me on 23 October and i told her that i would pay the outstanding amount in 2 months installment, she told me that its not allowed to pay cash and i disputed because according to the letter of demand that was sent me to me it had 3 options of payment which was cash, EFT or debit order, she shouted at me like i was her child and i ended up telling her that she must tell someone to call me since she is bullying me and i would not tolerate her to bully me, i have been MFC customer for a very long time and i only skipped one month . she said she will ask someone to call and make an arrangement with me the following day, today (22 October )early in the morning i receive a message to say my account has been handed to the outside debt collector and i would be liable for 10 percent interest, clearly MFC does not know how to deal with their clients and i regret for choosing to be financed by them and i would never encourage anyone to take finance with them. this is appalling, their employees are not trained well to deal with clients.