Unpleasant service i got at Pick n pay hyper Norwood mall

Went to pick n pay hyper Norwood mall to buy a phone for my niece day before yesterday..as the cashier was busy with the transaction she told me I have won then she called the supervisor to assist..the lady then said I should leave my contact details of which I did..then today early morning they called me to say I must come instore for my voucher..drove all the way from the south to Norwood mall only to be told something went wrong as there were helping me the lady said I'm supposed to get my 1000 rand voucher only if the cashier had not canceled the option..was then told to go back again they will call me once the matter has been finalized..my problem is why was I called in first place...wasted my time,my energy and petrol for nothing..plis look into this before I escalate it further