Hello Sagheer_hussain,
Thanks for posting in the Apple Support Communities.
We see you're looking to use Apple Pay, but see the attached screenshot when you try to add a card, correct?
If we understood this correctly, let's first make sure the latest supported iOS version is installed on your iPhone. If an update is available, be sure to back up your iPhone before installing it. For assistance with this, check out the following steps and you can locate additional steps here: Update your iPhone or iPad - Apple Support
Update your iPhone or iPad wirelessly
1. Back up your device using iCloud or your computer.
2. Plug your device into power and connect to the internet with Wi-Fi.
3. Go to Settings > General, then tap Software Update.
4. If you see more than one software update option available, choose the one that you want to install.
5. Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now. If you don't know your passcode, learn what to do.
If you have the latest supported iOS version, try changing your region to a different location then adjust it back to see if that clears up the message. To do this, you'll want to go to Settings > General > Language & Region. Let us know the results after trying this, and we'll pick up from there. This helps to determine if there may have been a disruption in the connection with the Apple servers.
Have a great day!