In Kingsman: The Secret Service, after the bar fight, Gallahad sends an "amnesia" dart to the barman who dialed a three-digit number, which I assume is the UK emergency number 999.
The barman then fell with the phone in his hand (next to his ear, which shows he was done dialing) and Gallahad went to finish his beer.
Shouldn't the call be followed-up by emergency services anyway? I believe that like in most countries calling a number and then not hearing the caller is a signal to urgently send someone to check.
Gallahad on the other hand was not particularly in a hurry to finish the beer and the conversation.
It may have also been a quick dial number to the mob, but the effect should be the same - someone seeing the call and then silence would likely send someone to check as well.