To the people saying those of us who don't find the cashier's behavior offensive are apathetic, no I'm not. If it was two cashiers talking to each other and not ringing me up because they're so busy with their conversation, I would definitely have a problem with that. That has happened to me- at Starbucks- and trust me, I complained directly to the two offenders and never went back.
But in the OP's scenario, the cashier went about her job of ringing the customer up. I'm assuming the OP was there for convenience sake and it doesn't sound like the phone call slowed the cashier down or inconvenienced the OP in any way so to me it's no big deal. I don't go to 7-11 or similar places for customer service. I don't get why anyone else would either.
But in the OP's scenario, the cashier went about her job of ringing the customer up. I'm assuming the OP was there for convenience sake and it doesn't sound like the phone call slowed the cashier down or inconvenienced the OP in any way so to me it's no big deal. I don't go to 7-11 or similar places for customer service. I don't get why anyone else would either.