Want to cancel the deal as i was given wrong deal but the MTN Savanna rude

App**** for 20G day and 20G night data deal on Tuesday at Savanna MTN store,not happy with what the store gave me and returned to the store to cancell the deal but they took me from pillar to post,this guy called Thabang is not cooperative and he is very rude,they did not give me even a reference number for the cancellation, Assist me with steps to take in order to get this deal cancelled