***** at Pep cell. Lusikisiki main road

I bought a cell phone at Pep cell Lusikisiki main. After 3 weeks using the cellphone, it was giving my sister problem when using it. It was not working when she is typing, sometimes when she make calls it cut off the call. She send back to Pep because it was still under warranty.... When she want to check it... They sad s b r must pay 3000.. 00mind that I bought with 1600.00 They gave her a cell no, she must call Samsung... She call no one pick the phone. We call head office, they sad they know nothing about money, but when she go to store (Pep at Lusikisiki Pep cell) they don't want to give her the phone, they want 3000.00 for repairing the phone. My question why she must pay 3000. 00 the phone is still under warranty. They don't answer, I must call the no or deposit the 3000.00 to that standard bank account. I feel ******, all I want is my phone, I can't pay 3000. Can Pep store assist me to get my phone back.