Do we really need to “Buy” Twilio phone number for testing a Rasa Bot with Twilio ?
Here the Step#3 :
Now you can use the Account SID , Auth Token , and the phone number you purchased in your credentials.yml .
Do we really need to purchase ? Can we not test whatsapp integration for free ?
Whatsapp has a closed API that requires either applying directly for access (only by medium/large businesses) or using providers like Twiliio. This isn’t something Rasa-related; it’s up to Twilio what their pricing scheme is. It looks like they do offer a free phase right now: twilio.com/docs/usage/tutorials/how-to-use-your-free-trial-account
Thanks a lot for the info, but unfortunately it didn’t help me much. I have such a problem that I want to register an account on the site, but without a mobile phone I cannot, unfortunately, do this. I decided to google what to do and came across this site verifywithsms.com . Thanks to him, I was finally able to register accounts without using a mobile phone, which I am incredibly happy about. I even told my best friend about it who had the same problem and now everything is fine! 
What if I have to use my phone number to register?
You can use an alternative method of protecting your account that they can offer you. If you doubt this method of protection, you can use the mobile app, with which you will solve your problem and not come back to this issue. I think there are already many people who want to secure themselves and their money, and there are probably more ways to solve this problem.