Fnb homeloans unprofessional

I have my homeloan with FNB MORE THAN 22 YEARS.THIS MONTH FNB HOMELOAN CALL me 2 days AFTER I SHORTPAY R68 .For only R68 they will call 4 to 5 times a day and send me threatening sms and emails.This is totally unprofessional from them as I am a client from FNB more than 25 and just Paid R68 short and then to received treatining emails and sms