Samsung s5 can't suddenly save the strange number entered into the keyboard or SMS. Why?

According to your description, if the phone can't store contacts, I suggest you:

1. If it cannot be stored on the SIM card, please check whether the contacts on the SIM card are full. If not, please try to replace the SIM card.

2. If it can't be stored in the mobile phone, you can check whether the memory of the mobile phone is full. I suggest you try deleting some software or multimedia files.

3. Open the phone settings-applications-(management applications)-contacts-try to clear the data.

4. Back up the data and try to restore the factory settings.

If the problem still exists, it is recommended that you take the purchase invoice, maintenance card and mobile phone to the local Samsung service center for professional engineers to help you test.

It is recommended that you apply for "booking to the store" in Samsung official website and enjoy priority maintenance service:/pre-order.

If you need help, please visit support.samsung.com.cn, and official website will provide you with multi-channel service support!