How to verify an account using SMS or Call

I am working on an eCommerce website but our client told us to add functionalists like they want to verify an user account by sms or by call.

I don't know how to do this and how many of websites and apps do this.

Do they use any third party services or can we implement it by our won?

If we have to use this service please tell me the name and how much it costs and how to setup?

If there is any alternative please tell em that also.

Moreover I want to use this services for testing also.

Any help would be appreciated.