My face time doesnot work with data it only works with WiFi so how can i change this

Have you followed the steps in the Related Article above to include going to Settings and tap Cellular or tap Mobile Data, then turn on FaceTime? If you're using an iPad, you might see Settings > Cellular Data.

Try a restart.

Restart your iPhone   *

Try a forced restart. See the section towards the end of the article.

Reset Device. -

If necessary

Hard reset.     -

Do a backup and try a factory reset. Then restore from the backup.

Restore to Factory setting.      *

Restore - If you see an error when you update or restore your iPhone, iPad, or iPod.   *

Backup - Restore your device from an iCloud or iTunes backup.     *