Foschini Cellphone

i bought a cellphone at Foschini in march and i only used it for 3 weeks then it was lockdown . on the 1st of May when they open i had to take it back as they have a 2 years warranty. since they booked it for repairs , and now in June they sent me a message that i must pay R3400 for the repairs . for which i dint understand , i just used my phone for 3 weeks and the fault was that it doesn't want to charge it keeps saying betry temperature is very low. how can i pay for something i did not even use for a month. please help me as i bought that phone on credit and now they want me to pay R3400 for repairs.