"I have his cellphone."
Translation:Ik heb zijn mobiele telefoon.
In Belgium both in French and Dutch they use the word GSM for all mobile phones. I do not know if in the Netherlands it is also used. But I know that it is not the case in France in French. Maybe it is only a Belgian thing.
According to Wikipedia: GSM (Global System for Mobile Communications, originally Groupe Spécial Mobile), is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe protocols for second-generation (2G) digital cellular networks used by mobile phones. As of 2014 it has become the default global standard for mobile communications - with over 90% market share, operating in over 219 countries and territories.