Repair cost for a phone still under guarantee

I got an samsung tab3 and recently recently as soon as i put it on charge the phone just went dead so because its under a year old and under guarantee i decided to took it in for repairs. The phone got a crack screen but it still function very well and i just need them to fix the problem with the charging. I give them a call today to find out how far are they with the repairs. I got a shock when the Kleinmond shop owner Dewald told me to fix the phone it will cost me R2200 cash. Why do i have to pay when the phone is still under guarantee and warranty i don't need the screen to be fix because it still work i only needs the charging problem to be fix....