Unhappy Customer

I took a personal loan with African Bank on 2017/12/08 , and told that since my first payment is on the 2018/01/12 l could not pay on the date as my pay day is on the 25 of every month.

I visited to branches to confirm that my first installment be on the 25 and the consultants said l should not l won't be in arrears they did not even bother to take my ID and check. Now I'm getting calls that lm behind my payments what kind of service is that being offered to a long time customer who never defaulted before , please fix this and stop calling me that l owe you