Saving contacts on Sim Card is very helpful when you change your phone. So, when you save a new number, you can save on Sim Card like these steps.
1. First, write the phone number you want to save.
2. Then, tap New Contact.
3. After that, write the name and tap Save Location.
4. Then, choose SIM card.
5. Next, tap Done; the number will save on your SIM card.
Besides that, you can read Steps to move contacts from Phone to Sim card. These steps will help you when you change your phone or when your phone is damaged.