Identity handed my paid up account over

I have paid my account up to date and identity keeps sending me sms's and calling me saying my account is in arrears. I have sent my bank statements serval times and called them but Noone seems to assist. My account is paid every month and I pay more than my installment. In March I had a balance of R350 which I paid before the due day and purchased. Every month I paid via my banking app using my ID number as my reference which was advised on my emails from them. Today's sms says I'm handed over for collections and charged interest. I want to now take the legal route and have this resolved. Identity can contact me on ***