The verb "interrompere" means interrupting the course of an action and that can happen deliberately or not. The applied translation "Terminata" sounds like the other person has intentionally hung up the call. Instead, "interrotta" followed by "all'improvviso" (unexpectedly) is more appropriate to use to refer to a call that stopped suddenly on a social media app. "Di colpo" is never used as a synonym of 'unexpectedly' when people are asked to give a technical feedback about similar issues.