I need an answer

I have a housing loan with FNB for more than 3 years what I do not understand is that my loan is deducted straight from my salary by payrolls since I made the as the partnership with my employer what I fail to understand this not the 1st time I get notified that my account is in arrears and payroll assured me that account is being paid faithfully every month how the hell is it possible for my account to go in arrears someone needs to answer