Wrong information

ITC BA are harassing me about alleged money owed to Lancet. They can't provide me with statements or invoices for these, just dated and amounts. They say I must get the statement from Lancet directly. When I received the statement from Lancet it bears no resemblance to the amounts ITC claims to be outstanding. I paid the amounts as per the statement and they (ITC) have the audacity to sent a sms to inform me I have short paid! When I phoned and asked how it is possible they said I must get a statement from Lancet because I owe more. I immediately phoned and received a new statement and in fact Lancet now owes me money yet ITC claims I have not paid the full amount and have listed me as a bad payer.<br> How can you list someone if you don't even have the correct information to start with?