Cancelled bank card

My wife has a savings account with Nedbank which she doesn't use regularly the other day we tried to use the account to our surprise the account was closed. we contacted Nedbank and was informed that the account was closed because its not frequently use.

why close an account that has a positive balance without informing the account holder we spoke to a service consultant yesterday and we have since been waiting for their call now we cant even use our own money

this is unacceptable as a customer I need answers