Elderly customer threatened with account freezing

My elderly mother received an sms to provide FICA documents at her branch within 5 days to avoid her account being frozen. She has no transport and is not computer literate. She phoned me in panic that her account is going to be frozen and she has no idea what to do. Fortunately, I have power of attorney so I could make enquiries. I found out from customer care that the sms is in fact legit. I thought it might be a hoax because of how unreasonable it was. They gave me a number (***) to find out exactly what is required, but I cannot get through. I've been kept on hold all morning. I cannot contact her branch directly as there is no direct number available to customers. I emailed a copy of her ID and proof of address to customer care and *** with no acknowledgement of receipt as yet. She does not live with me, so I sent through the only documents I could access. I have no idea why she in particular received the sms. I am an fnb customer and did not get the sms. My husband who uses another bank has received no such requirement from his bank. So why? . I understand that FICA requirements are law, but if you are updating your system with people's details, at least notify the public in advance, through a clear message that this needs to happen and why and what will required of them. Give people a reasonable amount of time to comply. I find fnb's decisions and methods in this regard to be unreasonable. I have no idea if the documents I sent actually comply but if my mother's account is frozen for circumstances beyond her control, I will consider removing all her money from FNB. We have choices on banks and we want a bank that gives reasonable, considerate services.