Can the bank do this? UK?

I borrowed some money from a Payday company but then lost my job. I contacted the company and told them I would pay the money back so much a month. They declined and wanted me to pay more a month which I could not afford. I have a key account at the COOP Bank which states I am not allowed to go overdrawn. I have no money in the account but I have just found out that they have paid this company �46 and made me overdrawn? I contacted the Bank and said there is nothing they can do because this company has my details and I cannot close the account till I pay the bank what I owe them. How can they do this when it states on my contract that I can't have an overdraft? I cannot afford to pay the bank so that means this company can dip in and out whenever it feels like and I will end up with extortionate fees? What can I do?