MRP don't care about their clients and DO NO RESPOND to any form of contact

I have been a loyal customer for over 15 yrs and have paid my account as per statement received every single month as statement suggested the amount due is. Suddenly I get bombarded with sms that I am in arrears, WTH???!!! So I called them and they had alook and they stated that I am not in arrears as they did receive my full payment as per my Aug statement. and that this must be a technical error. I told them to rectify this immediately! AND nothing was done as I got an sms again telling me I am in arrears so I went into their store and asked to check my balance to see if i am in arrears and again NOTHING I am 100% up to date! I even bought stuff on credit the same day for my daughter! Now I was sent my September statement and guess what I am in arrears WHAT BULL.... is this ??? I have emailed x5, called them, even FB messaged and FB post them but NO one responds.

I will not except this and I want their HO to contact me ASAP or I will close my account and will tell all my friends, family not to support MRP anymore.