I am unable to check for update

Which update are you referring to? 

• iOS Update? Which Version? Update your iPhone, iPad, or iPod touch - Apple Support
• Carrier Update? Contact Carrier. Update your carrier settings on your iPhone or iPad - Apple Support
• App Update? Which App? Contact App Developer? How to contact an app developer - Apple Support

You may get better and prompt responses if you may kindly provide the iPhone Model that you have and the iOS version if it is known to you.