Normally I try to tune out obsessive smartphone users but when they are customers in my store, unfortunately I have to deal with this. It really pisses me off when they're jabbering away on their damn phones at the same time I'm trying to help them. Oftentimes they hold up the line while they're doing this. It disrespects everyone in the store - employees and fellow customers alike.
Of course this would be illegal but it's at times like this when cellphone jamming devices would be a godsend.