It's not true. I did quick search and found one which claim they give free course and certificate, simplilearn[dot]com/learn-blockchain-basics-skillup. Take note i don't know good or reputable is that website.
Alright, i just checked the site and they referred me to a four month program with Indian institute of technology kanpur starting Nov 2nd and they are asking for my phone number during registration. is that safe?
As i said previously, i don't know good/reputable is that website. But based on your experience so far and reading few 1-4 stars review on trustpilot, personally i'd avoid such website when free and reputable learning resource is available.