Change of banking details via call center

Telkom has once again has disappointed me, I love the network so much and understand its disadvantages e. g not having coverage in certain areas Now my issue is that i contacted customer care (Telkom) 9 days before my pay date to let them know i changed banking details for the debit i have they did not change it nor give me feedback however i was assured it was done imagine if the debit had bounced backwhile i did informed Telkom to change am really disappointed if it takes more than 9days to change just an account no on your system i understand but just make me aware to leave enough funds or something and confirm when it will be switched.