Why Iam not able access camera on messages and not able see mms on / off option

Hello sumanth208,

Welcome to Apple Support Communities!

We can understand wanting to use SMS and have the camera working for you messages as well.

For the SMS concerns, this has more details:

"To use SMS/MMS on an iPhone, you need a text-messaging plan. Contact your wireless carrier for more information. You can also set up your other Apple devices to send and receive messages from any Apple device."

You'll want to contact your carrier to discuss your SMS plan, detailed here: What is the difference between iMessage and SMS/MMS? - Apple Support

For the camera issue, does the camera work normally in other apps? Start here:

"Remove case, accessory, or film and test

1. Remove any case, accessory, or film that might block the camera or flash or that places a magnet near the camera.
2. Test the camera by trying to take a photo.
3. Test the LED flash:
   1. Try the flashlight in Control Center on your iPhone or Control Center on your iPad. On an iPhone X or later or an iPad, swipe down from the upper-right corner of the screen. On an iPhone 8 or earlier, swipe up from the bottom edge of any screen.
   2. Tap the Flashlight button ."

This Apple Support page has the full details and additional steps to take: If the camera or flash on your iPhone, iPad, or iPod touch isn't working - Apple Support

We hope this helps to isolate and resolve both issues so you can use your iPhone as expected when using SMS and the camera.

Cheers!