FNB *****ing from Consumer

Today, i got sms of money debited off my account for R1739. there was no reference or anything, but later i got sms from FNB saying the money has been deducted due to arrears on my account. no prior warning, only after the fact. i January 30th, i have received the same message after R4428 was debited off my account and there was no-way of returning this as it is an internal debit. i have been making the payments to my loan and the number on the sms is for the collection agencies, not fnb.