how to transfer sms from android device once iPhone is already setup

Hey there and welcome to Apple Support Communities ManojAriyamparambath,

We can certainly understand your concern and see you came to us from the article If you can't send or receive messages on your iPhone or iPad.

Message data should have transferred using the Move to iOS application. That being said, we recommend checking out these steps for more information on how to transfer data from Android to iOS and see if it matches up with your procedures.

" Ready to transfer to iOS? Download the Move to iOS app to get help switching from your Android device to your new iPhone, iPad, or iPod touch.

Get Move to iOS from Google Play

If you can't use the Google Play Store, learn how to download Move to iOS.

Before you begin

• On your Android device, make sure that Wi‑Fi is turned on. 
• Plug your new iOS device and your Android device into power.
• Make sure that the content you're moving, including what's on your external Micro SD card, will fit on your new iOS device
• If you want to transfer your Chrome bookmarks, update to the latest version of Chrome on your Android device.

1. Get started on your Apple device

Turn on your new Apple device and place it near your Android device.

On your Apple device, follow the onscreen setup instructions.

On the Quick Start screen, tap Set Up Manually, then continue to follow the onscreen instructions. You might be asked to activate your eSIM.

2. Tap Move Data from Android

Look for the Apps & Data screen. Then tap Move Data from Android. (If you already finished setup, you need to erase your iOS device and start over. If you don't want to erase, just transfer your content manually.)

3. Open the Move to iOS app

On your Android device, open the Move to iOS app. If you don't have the Move to iOS app, you can tap the QR code button on your new iOS device and scan the QR code using the camera on your Android device to open the Google Play Store. Tap Continue, and read the terms and conditions that appear. To continue, tap Agree.

4. Wait for a code

On your iOS device, tap Continue when you see the Move from Android screen. Then wait for a ten-digit or six-digit code to appear. If your Android device shows an alert that you have a weak internet connection, you can ignore the alert.

5. Use the code

Enter the code on your Android device.

6. Connect to a temporary Wi-Fi network

Your iOS device will create a temporary Wi-Fi network. When asked, tap Connect to join that network on your Android device. Then wait for the Transfer Data screen to appear.

7. Choose your content and wait

On your Android device, select the content that you want to transfer and tap Continue. Then—even if your Android device shows that the process is complete—leave both devices alone until the loading bar that appears on your iOS device finishes. Keep your devices near each other and plugged in to power until the transfer completes. The whole transfer can take a while, depending on how much content you're moving.

Here's what gets transferred: contacts, message history, camera photos and videos, photo albums, files and folders, accessibility settings, display settings, web bookmarks, mail accounts, WhatsApp messages and media, and calendars. If they're available on both Google Play and the App Store, some of your free apps will also transfer. After the transfer completes, you can download any free apps that were matched from the App Store.

8. Set up your iOS device

After the loading bar finishes on your iOS device, tap Done on your Android device. Then tap Continue on your iOS device and follow the onscreen steps to finish setup for your iOS device.

9, Finish up

Make sure that all of your content transferred. Music, books, and PDFs need to be moved over manually.

Need to get the apps that were on your Android device? Go to the App Store on your iOS device to download them.

If you need help with the transfer

• Make sure that you leave both devices alone until the transfer finishes. For example, on your Android device, the Move to iOS app should stay onscreen the whole time. If you use another app or get a phone call on your Android before the transfer finishes, your content won't transfer.
• On your Android device, turn off apps or settings that might affect your Wi-Fi connection, like the Sprint Connections Optimizer or the Smart Network Switch. Then find Wi-Fi in Settings, touch and hold each known network, and forget the network. Then try the transfer again.
• Restart both of your devices and try again.
• On your Android device, turn off your cellular data connection. Then try the transfer again "

For additional information, check out this link: Move from Android to iPhone, iPad, or iPod touch - Apple Support

Kindest regards!