Is it legal for banks to charge SMS notification fees?

It was found that there was a three-month "short deduction" fee for 2 yuan in the passbook every month. After consulting the Postal Savings Bank, I was told that "short deduction" is the deducted "SMS fee". Ms. Zhu said that although 6 yuan was the only one who was detained, the Postal Savings Bank made her feel very uncomfortable. Because she didn't subscribe to this short message service actively, but the Postal Savings Bank subscribed for her without her knowledge, she felt that it was very wrong to be deducted from the "short message fee". "In our community, there are still many residents who have been deducted from the' SMS fee' at the Postal Savings Bank like me." What is even more ridiculous is that an old lady near Ms. Zhu's home doesn't even have a mobile phone, and the Postal Savings Bank actually deducts the "SMS fee" from her 2 yuan money every month.