Hello valeriyValVal,
Your iPhone doesn't store contacts on the SIM card, so let's take a look at other possibilities. If you'd like to learn about where your contacts are stored, check this out: Import contacts from your SIM card to your iPhone
Contacts are stored either on your iPhone or in the cloud. Did you recently change or sign out of any of your email accounts? If you sign in to iCloud, are you able to see all of your contacts?
It is also a good idea to make sure that your device is up to date. You can learn how to create a backup and update your iPhone here: Update your iPhone, iPad, or iPod touch
Cheers!