Updating of Contact Details

I have a new cell number and went to Nedbank branches in Clearwater Mall, Nicolway and Stellenbosch to have my details updated... After every visit I was assured that the system is updated, yet I still receive updates on my old number... The old number will stop working by the end of the week and I cannot afford to waste more of my time on this... Please advise who can assist me with this without me having to waste another 30 minutes in one of your branches with their ineffective ticketing system...