Pathetic service from Lancet accounts department

My wife went for some tests Feb 2021. She got the invoice and I paid it. Some weeks later they send me that same invoice with the same procedures on it. The only difference is that the second invoice has inflated prices on it. some of those procedures were up to 60% more expensive on the second invoice. I refuse to pay the difference . I have explained the situation a thousand times to different people from their accounts department and their collectors. It seems as if they only employ idiots in those two departments. They just don't listen to what I have to say and they don't have an explanation why the same procedures cost different on different invoices.