aircon

Q: I purchased a second hand aircon from a fellow Muslim brother. He promised me that its works perfectly. I took his word on it and paid him R2000.00 to install it. R1500 for the unit and R500 for installation. However the aircon did not work from day 1. I kept on messaging him for 2 months that its not working but he kept insisting it is and he continued ignoring my messages. I got fed-up and asked him to please remove it as its not working. Without my knowledge he came to the house after the 2 month period when my dad was there to repair it, and he admitted to my dad its not working. He said he will bring the parts to repair however I told him to remove it. He then took 3 weeks to come and remove it and told my dad he will do a bank transfer for the refund. A week later after messages after messages he only refunds me R1000.00 and tells me that because of his time and labour he is only refunding half my money. When I explained to him the unit costs R1500.00 as per his invoice he said no the unit was R1000.00 but when I sent him a picture of his invoice he admitted its R1500.00 and he will only refund the R500.00. It is now gone a week and he has gone back to ignoring my messages and no refund has been received. I ask you respected mufti, what must the total refund be? Should it not be for the full R2000.00 because the aircon did not work at all. Can I lay a charge of theft against this person.