Arbitrary reduction of credit limit

I have banked with FNB for about 40 years, since the days it was Barclay and have a bond, cheque account, credit card and investments with them. My credit card is paid in full every month. All my accounts are in excellent standing. i received the following no reply sms from them, \Due to responsible lending we have systematically adjusted your limit on your FNB credit card from *** to ***"end of message. This represents a 60% reduction in credit limit. No phone call nothing just this sms. I have a personal banker also"