Bad service no response to emails or calls

I took out a small loan with mobicred. All was fine until I changed my banking account. They can’t seem to pick up my payments. I get threatened. I have send proof of payment I don’t even know how many times. No one responds. I phone I can’t through. Now they have taken me the lawyers. I send mobicred and the lawyers proof of payment. Nothing happens. This is in December. I can the lawyers they said they will make a note but said need to go to Mobicred. So I said can I send proof of payment. The guy irritated wandered yes. Send them and mobicred another email with proof of payment. I hear nothing back. Until now Mobicred asks me for my ID. No problem send it to them. Have send it more often but no response. Then says no I need to deal with the lawyers. I have continued to pay them monthly. But there statement is completely off. I am so angry I am being send backwards and forwards. I don’t know what to do. I am not paying them the whole lumps on as I have been paying them. I changed accounts but the bank took all information from my old account and put it onto my new account. The banking details are in order. Just now they blacklist me what can I do!!!!! Their service is absolutely **********!