Rude manager who doesn't want to exchange my phone

Went to a Pep cell in mama mall next to Shoprite,I have never in my life thought I would meet such an arrogant, disrespectful and pathetic manager. So I went there to report my phone as the phone has been giving me issues when trying to use the apps and also would randomly kick me off the server while using Chrome. The phone was bought the 29th March n I went there the 03rd April to ask for an exchange or if possible a different model. When I got there the cashier was the sweetest, asked the store manager Tsakane who from the onset was rude to assist. Tsakane swear at me , told me how I'm being childish when she was assisting me when she refused to take the phone back because according to her the phone is perfectly fine and she will never exchange it even if it means I'll sleep at the store. Ok she even as far as asking the security guards to escort us out of the store as she was closing n she will never assist unless I buy a memory card that time the phone is only at 64,% for storage