My mother's phone turned into a text message reminder.

I haven't heard of this kind of problem. But we can solve it by elimination. Try to format the phone and restart it. If not, it's a software setup problem. If the mobile phone has a mobile phone card inserted, it is a card problem, but this is a mobile phone problem. Contact the place of sale or manufacturer to return the goods. Mobile phone cards are not accepted. Go to the business hall to handle it. The same method can also be used on your mother's mobile phone.

I hope I can help you.