No justified reason for locking my account

I have a credit card with Discovery bank, I have been making payments monthly into this account. I did change jobs a few months ago and my salary date changed from the 25th to the month end for 6 months The pay date will change again once my probation is over, I have been missing my 25th pay date into the account but have been making my payments on the last day of the month every single month. This month I have gotten threating emails, advising that my account is in arrears and I must make urgent payments. I paid a double installment at the end of the month and I am now getting hounded by the call center and my account has been locked, I spoke to 2 agents and they cannot understand how this account has been locked and escalated to them when the account is not in arrears. Its infuriating because I am left with an effected credit score, I have to get threatening notifications and embarrassing phone calls while I'm at work but there is no real reason for it from the company's side either. the level of unprofessionalism is unreal