Harrasment for inaccurate billings

Lancet accounts department consist of rude and *********** staff. My mum is a warfarin patient and I manage the payments of her account once her savings are depleted. I am constantly harassed by sms , email and calls for payments that have already been made. The behaviour of their personnel makes me wonder if Lancet incentivise their staff to be rude, arrogant and display short of harassment behaviour. I have paid all my mums accounts and keep getting bills, with varying amounts from week to week. Some with amounts from 3 years back. I refuse to make any payments when Lancet cannot give me a comprehensive statement showing all tests and all payments received. They keep sending me references and amounts but no history trail. I have the history luckily from my medical aid and my cash payments and know that they are talking *******. Thus I refuse to make any further payments to such an *********** organisation and I would appreciate if they can stop harassing people for money that has already been paid!!!!! Get your company in order. Lancet billing is pathetic and short of theft!!!