Called failed when making call from Watch

Hi, poonam3!

Thanks for visiting the Apple Support Communities! I understand that you're having issues making calls from your Apple Watch Series 5. When you try, you get an error that the call failed. I'm happy to help!

First, check for--and install--any available updates for both your Apple Watch: Update your Apple Watch - Apple Support and its companion iPhone: Update your iPhone, iPad, or iPod touch - Apple Support.

After updating, see if you're able to make calls from your Apple Watch. If not, reset the network settings on your iPhone by going into Settings > General > Reset > Reset Network Settings. This step shouldn't remove any of your personal data, but it will remove saved Wi-Fi networks, as well as any previously connected APN or VPN settings.

Should you still be unable to make a call from your watch, try unpairing it from the companion iPhone: Unpair and erase your Apple Watch - Apple Support then setting it up again: Set up your Apple Watch - Apple Support.

Best!

Hello again, poonam3!

Thanks for letting us know that you're able to make calls with your Apple Watch now. It was our pleasure to assist!

Have a wonderful day.