Valve is trying to end account smurfing in 'Dota 2'
 

Valve is changing the way Dota 2 is played, at least on a meta level. Beginning May 4th, players will be required to register a unique phone number to their accounts in order to queue up for ranked matches. That's one account per phone number, ostens...

https://www.engadget.com/2017/04/21/...ing-in-dota-2/