Cellphone purchase

I purchased a cellphone and lost my receipt right,however I have bak statement that proves my cellphone purchase,went to Mr Price and the service I received there was very dissapointing, they could not assist me without the receipt however I once purchased an item and upon exchanging it I was asked to produce a bank statement and I was assisted. So this time when I went with the bank statement I could not be helped and was advised to speak to the area manages,it's over a month now and the shops area managerhas not gotten back to me. It's a brand new phone that keeps on freezing.mr Price Cresta is ***