Can't do there job properly

Whet to buy 8/1/16 airtime asked for R160 MTN and was told they had R180 I then rep**** I want R160 they sign and then I told them you can make it up by 2x R60 a 1x R30 and 1x R10 why should I think for someone that should know how to do there job correctly if they can't they in the wrong job after all this a god mad and asked for the manager then both cashiers laughed and then I got more furious manager came the cashier gat me a R160 MTN airtime and it was not even broken down to 2x R60 1x R30 1x R10 it was R160 why should I make a fight of something and in the end I got what I asked for but my blood pressure was raised for nothing why waist my time like that I always put petrol in there and first time in the shop why must we get bad service I'm in retail and I can't allow my people to laugh at people it's rude and uncalled for please take your people for client service lessons as they are not trained at all in that area