Nedbank obtaining client's phone number without permission

My Nedbank account is linked to my wife's number. Having been stuck overseas, I bought a new sim-card for myself with a new number at the airport ion 18 December. In December, I gave that number to my wife, my dentist and our vet. I never went to Nedbank or used online banking or contacted them with this new number On 2 February I received a very strange sms on this new number. From Nedbank, informing me that my celphone was changed in my profile. Astonishingly, the mail informs me that it was changed from my own new number, that Nedbank has no way of knowing, to a completely unknown number... A number was also given for questions. I called it and read out the sms and a very friendly lady was totally confused. She confirmed that the only number in my profile is my wife's number, that these two numbers appear nowhere in my profile - but also that Nedbank did indeed send that sms... After trying for 30 minutes to figure out where the sms came from, she told me she would call me when she had news. But I received no update. My question is not about an sms that could be a mistake or a computer error. My question is how Nedbank can get hold of a new phone number of a client who has not given them that phone numver? Whoever is involved is highly *********.