[Gmail] Calling in Hangouts will be turned off soon.

If you recently logged into your Gmail account you must have seen the above message stating callings in Hangouts will be turned off soon, as you must have used Hangouts to call international and domestic phone numbers before this will not be possible from early 2021 if you read Google's official article

If you are in the US, you can continue to make phone calls by upgrading to Google Voice. If you are not in the US or do not want to upgrade to Google Voice, you can continue to use the Hangouts call phones feature until late 2020 with access to classic Hangouts. You can also request a refund of your eligible calling credit.

https://support.google.com/hangouts/answer/3187125?hl=en

Google Voice:

Google Voice lets you send text messages from your computer to any mobile phone, it lets you read your voicemails and make international calls at low rates. You can block unwanted callers and see the caller details when you receive a call.