Where has the common decency gone to in some people?
It is only courteous when in the presence of another person that one does not spend a considerable amount of time on their mobile phone. It is increasingly common these days that people would rather spend time looking down at their phones than having a face-to-face conversation.
If you have something that urgent to check on your mobile phone, excuse yourself and apologise. I think that especially in a one-on-one situation it is a lack of respect to the other person.
Have some manners, please.