How to restore contacts on iphone

I'd like to recommend you using a data backup tool,
Transfer Contacts from Android to PC

with this, you can selectively choose the contacts to backup, which allows preview.
And you can sync many other data, too.

Open a phoen transfer tool, connect both the phones to your computer and click start transfer. Phone numbers, photos, songs, videos and other media files are moved to your new phone. See more,
MobiKin Transfer for Mobile

If you have synced your iPhone XS Max to iCloud, it would be easier for you to retrieve deleted contacts from iCloud for iPhone XS Max and other iPhone models. The below steps would show you how to restore contacts you have deleted from iPhone XS Max from iCloud for your iPhone XS Max and other iPhone models.

1.On your computer, open icloud.com and log in with your Apple ID account.
2.Go to Settings tab on iCloud.com, then click "Restore Contacts" (in the Advanced section).
3.Then, you will see available versions listed by the date and time they were archived previously.
4.To the right of the version you want to restore, click Restore option.
5.Wait until iCloud finishes restoring your contacts before you change them. While it's restoring them, any changes you make aren't saved.
The restored contacts and contact groups will appear on all your devices set up for iCloud Contacts. If you haven't set up your iPhone XS Max for iCloud, on your iPhone XS Max, go to Settings > [your name] > iCloud, swipe Contacts option to green on the "iCloud" window, and then click "Merge" button. You could then view all restored contacts on your iPhone XS Max.
Actually, with iCloud, you can restore your contacts, calendars and reminders, or Safari bookmarks and reading list from an earlier version that was automatically archived in iCloud. However, restoring contacts for iPhone XS Max and other iPhone models requires you to have archived contacts to iCloud.com previously. Otherwise you won't be able to retrieve contacts from iCloud.com.

For more methods, check: How to Recover Contacts from iPhone XS Max/XS/X

Do you close open apps? Double click the home button and a small bar will come up on the bottom, you should delete everything in that bar. Your phone might have been running too much at one time and that may be why it happened. Your information should automatically be backed up on your computer's itunes or icloud though.

You should be able to right click on your iPhone in iTunes and click restore from backup, there may be a backup that is older that you can restore from, other than that no backup of your contacts is stored.

Try this:

1. Open iTunes on your computer.
   

2. Plug in your iPhone to your computer just as you would to sync it normally.
   

3. Locate the iPhone in the "Devices" column at the left of the iTunes application window.
   

4. Right-click (Ctrl + click for Mac) on the iPhone icon in the "Devices" column and select "Restore From Backup." Select one of the backup versions from the drop-down menu and click the "Restore" button. This will restore any contacts that you have lost since your last sync in iTunes.
   

5. Eject your iPhone and go to your contact list on it. Any lost contact or contacts should be restored to your list.
   

Read more: How to Recover Lost Contacts on an iPhone ' eHow.com http://www.ehow.com/how_5651802_recover-lost-contacts-iphone.html#ixzz1AofqMY96

try restoring your iphone with itunes, but first backup all your needed data. AND be sure your iphone is not jailbroken or have done any hacks to it because restoring it in itune would cause the iphone reset to its factory stae, thus losing all the data, and hacks if you have any(including unlocking) and you might end up doing all again(hacks/unlocking), but if you have done no hacks or unlocking to it, go ahead and fire it up, restore using itunes, and youre good to go.