Harassment!!!

I have a personal loan with DA. My account is, as always, up yo date as payments are made via debit order. However, for some or other reason, they insist thay my account is in arrears for a month, in an amount not even remotely close to the installment amount. They phone me 15 - 20 times a day. I have explained myself over 10 times. They still phone. They start at 7 in the morning and continue until past 8 at nihht. They can not explain the allegef arrears to me and the mail addresses they give where I want to send my proof of payments are incorrect. They have not forwarded me a statement in two years. I am done being harassed. I will have no option but to seek a protection from harassment order from a competent coury in thid regard. They have me crying from frustration over an account that us NOT in arrears. I can't no more.